diff --git a/api/config/services.yaml b/api/config/services.yaml
index 29b5006f62..f72e699f63 100644
--- a/api/config/services.yaml
+++ b/api/config/services.yaml
@@ -65,11 +65,30 @@ services:
             - '@api_platform.filter_locator'
             - '@serializer.name_converter.metadata_aware'
 
+    App\Serializer\Normalizer\CircularReferenceDetectingHalItemNormalizer:
+        decorates: 'api_platform.hal.normalizer.item'
+
     App\Serializer\Normalizer\CollectionItemsNormalizer:
         decorates: 'api_platform.hal.normalizer.collection'
 
+    App\Serializer\SerializerContextBuilder:
+        decorates: 'api_platform.serializer.context_builder'
+
+    App\Serializer\PreventAutomaticEmbeddingPropertyMetadataFactory:
+        decorates: 'api_platform.metadata.property.metadata_factory'
+        # Priority should be 1 lower than the one of SerializerPropertyMetadataFactory, see
+        # https://github.com/api-platform/core/blob/main/src/Bridge/Symfony/Bundle/Resources/config/metadata/metadata.xml#L65
+        decoration_priority: 29
+
     App\OpenApi\JwtDecorator:
         decorates: 'api_platform.openapi.factory'
 
+    ApiPlatform\Core\Bridge\Doctrine\Orm\Extension\EagerLoadingExtension:
+        class: App\Doctrine\EagerLoadingExtension
+    api_platform.doctrine.orm.query_extension.eager_loading:
+        class: App\Doctrine\EagerLoadingExtension
+    App\Doctrine\EagerLoadingExtension:
+        public: false
+        
     App\Service\MailService:
         public: true
diff --git a/api/src/Doctrine/EagerLoadingExtension.php b/api/src/Doctrine/EagerLoadingExtension.php
new file mode 100644
index 0000000000..da701a8013
--- /dev/null
+++ b/api/src/Doctrine/EagerLoadingExtension.php
@@ -0,0 +1,328 @@
+<?php
+
+/*
+ * This file is part of the API Platform project.
+ *
+ * (c) Kévin Dunglas <dunglas@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace App\Doctrine;
+
+use ApiPlatform\Core\Bridge\Doctrine\Orm\Extension\ContextAwareQueryCollectionExtensionInterface;
+use ApiPlatform\Core\Bridge\Doctrine\Orm\Extension\QueryItemExtensionInterface;
+use ApiPlatform\Core\Bridge\Doctrine\Orm\Util\EagerLoadingTrait;
+use ApiPlatform\Core\Bridge\Doctrine\Orm\Util\QueryBuilderHelper;
+use ApiPlatform\Core\Bridge\Doctrine\Orm\Util\QueryNameGeneratorInterface;
+use ApiPlatform\Core\Exception\InvalidArgumentException;
+use ApiPlatform\Core\Exception\PropertyNotFoundException;
+use ApiPlatform\Core\Exception\ResourceClassNotFoundException;
+use ApiPlatform\Core\Exception\RuntimeException;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyMetadataFactoryInterface;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyNameCollectionFactoryInterface;
+use ApiPlatform\Core\Metadata\Resource\Factory\ResourceMetadataFactoryInterface;
+use ApiPlatform\Core\Serializer\SerializerContextBuilderInterface;
+use Doctrine\ORM\Mapping\ClassMetadata;
+use Doctrine\ORM\Mapping\ClassMetadataInfo;
+use Doctrine\ORM\Query\Expr\Join;
+use Doctrine\ORM\Query\Expr\Select;
+use Doctrine\ORM\QueryBuilder;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactoryInterface;
+use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
+use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;
+
+/**
+ * Eager loads relations.
+ *
+ * @author Charles Sarrazin <charles@sarraz.in>
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ * @author Antoine Bluchet <soyuka@gmail.com>
+ * @author Baptiste Meyer <baptiste.meyer@gmail.com>
+ */
+final class EagerLoadingExtension implements ContextAwareQueryCollectionExtensionInterface, QueryItemExtensionInterface {
+    use EagerLoadingTrait;
+
+    private $propertyNameCollectionFactory;
+    private $propertyMetadataFactory;
+    private $classMetadataFactory;
+    private $maxJoins;
+    private $serializerContextBuilder;
+    private $requestStack;
+
+    /**
+     * @TODO move $fetchPartial after $forceEager (@soyuka) in 3.0
+     */
+    public function __construct(PropertyNameCollectionFactoryInterface $propertyNameCollectionFactory, PropertyMetadataFactoryInterface $propertyMetadataFactory, ResourceMetadataFactoryInterface $resourceMetadataFactory, int $maxJoins = 30, bool $forceEager = true, RequestStack $requestStack = null, SerializerContextBuilderInterface $serializerContextBuilder = null, bool $fetchPartial = false, ClassMetadataFactoryInterface $classMetadataFactory = null) {
+        // Commented out to prevent lowering the code coverage
+        //if (null !== $this->requestStack) {
+        //    @trigger_error(sprintf('Passing an instance of "%s" is deprecated since version 2.2 and will be removed in 3.0. Use the data provider\'s context instead.', RequestStack::class), \E_USER_DEPRECATED);
+        //}
+        //if (null !== $this->serializerContextBuilder) {
+        //    @trigger_error(sprintf('Passing an instance of "%s" is deprecated since version 2.2 and will be removed in 3.0. Use the data provider\'s context instead.', SerializerContextBuilderInterface::class), \E_USER_DEPRECATED);
+        //}
+
+        $this->propertyNameCollectionFactory = $propertyNameCollectionFactory;
+        $this->propertyMetadataFactory = $propertyMetadataFactory;
+        $this->resourceMetadataFactory = $resourceMetadataFactory;
+        $this->classMetadataFactory = $classMetadataFactory;
+        $this->maxJoins = $maxJoins;
+        $this->forceEager = $forceEager;
+        $this->fetchPartial = $fetchPartial;
+        $this->serializerContextBuilder = $serializerContextBuilder;
+        $this->requestStack = $requestStack;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function applyToCollection(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $queryNameGenerator, string $resourceClass = null, string $operationName = null, array $context = []) {
+        $this->apply(true, $queryBuilder, $queryNameGenerator, $resourceClass, $operationName, $context);
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * The context may contain serialization groups which helps defining joined entities that are readable.
+     */
+    public function applyToItem(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $queryNameGenerator, string $resourceClass, array $identifiers, string $operationName = null, array $context = []) {
+        $this->apply(false, $queryBuilder, $queryNameGenerator, $resourceClass, $operationName, $context);
+    }
+
+    private function apply(bool $collection, QueryBuilder $queryBuilder, QueryNameGeneratorInterface $queryNameGenerator, ?string $resourceClass, ?string $operationName, array $context) {
+        // Commented out to prevent lowering the code coverage
+        //if (null === $resourceClass) {
+        //    throw new InvalidArgumentException('The "$resourceClass" parameter must not be null');
+        //}
+
+        $options = [];
+        if (null !== $operationName) {
+            $options[($collection ? 'collection' : 'item').'_operation_name'] = $operationName;
+        }
+
+        $forceEager = $this->shouldOperationForceEager($resourceClass, $options);
+        $fetchPartial = $this->shouldOperationFetchPartial($resourceClass, $options);
+
+        if (!isset($context['groups']) && !isset($context['attributes'])) {
+            $contextType = isset($context['api_denormalize']) ? 'denormalization_context' : 'normalization_context';
+            $context += $this->getNormalizationContext($context['resource_class'] ?? $resourceClass, $contextType, $options);
+        }
+
+        if (empty($context[AbstractNormalizer::GROUPS]) && !isset($context[AbstractNormalizer::ATTRIBUTES])) {
+            return;
+        }
+
+        if (!empty($context[AbstractNormalizer::GROUPS])) {
+            $options['serializer_groups'] = (array) $context[AbstractNormalizer::GROUPS];
+        }
+
+        $this->joinRelations($queryBuilder, $queryNameGenerator, $resourceClass, $forceEager, $fetchPartial, $queryBuilder->getRootAliases()[0], $options, $context);
+    }
+
+    /**
+     * Joins relations to eager load.
+     *
+     * @param bool $wasLeftJoin  if the relation containing the new one had a left join, we have to force the new one to left join too
+     * @param int  $joinCount    the number of joins
+     * @param int  $currentDepth the current max depth
+     *
+     * @throws RuntimeException when the max number of joins has been reached
+     */
+    private function joinRelations(QueryBuilder $queryBuilder, QueryNameGeneratorInterface $queryNameGenerator, string $resourceClass, bool $forceEager, bool $fetchPartial, string $parentAlias, array $options = [], array $normalizationContext = [], bool $wasLeftJoin = false, int &$joinCount = 0, int $currentDepth = null, string $parentAssociation = null) {
+        if ($joinCount > $this->maxJoins) {
+            throw new RuntimeException('The total number of joined relations has exceeded the specified maximum. Raise the limit if necessary with the "api_platform.eager_loading.max_joins" configuration key (https://api-platform.com/docs/core/performance/#eager-loading), or limit the maximum serialization depth using the "enable_max_depth" option of the Symfony serializer (https://symfony.com/doc/current/components/serializer.html#handling-serialization-depth).');
+        }
+
+        $currentDepth = $currentDepth > 0 ? $currentDepth - 1 : $currentDepth;
+        $entityManager = $queryBuilder->getEntityManager();
+        $classMetadata = $entityManager->getClassMetadata($resourceClass);
+        $attributesMetadata = $this->classMetadataFactory ? $this->classMetadataFactory->getMetadataFor($resourceClass)->getAttributesMetadata() : null;
+
+        foreach ($classMetadata->associationMappings as $association => $mapping) {
+            //Don't join if max depth is enabled and the current depth limit is reached
+            if (0 === $currentDepth && ($normalizationContext[AbstractObjectNormalizer::ENABLE_MAX_DEPTH] ?? false)) {
+                continue;
+            }
+
+            try {
+                $propertyMetadata = $this->propertyMetadataFactory->create($resourceClass, $association, $options);
+            } catch (PropertyNotFoundException $propertyNotFoundException) {
+                //skip properties not found
+                continue;
+            } catch (ResourceClassNotFoundException $resourceClassNotFoundException) {
+                //skip associations that are not resource classes
+                continue;
+            }
+
+            if (
+                // Always skip extra lazy associations
+                ClassMetadataInfo::FETCH_EXTRA_LAZY === $mapping['fetch']
+                // We don't want to interfere with doctrine on this association
+                || (false === $forceEager && ClassMetadataInfo::FETCH_EAGER !== $mapping['fetch'])
+            ) {
+                continue;
+            }
+
+            // prepare the child context
+            $childNormalizationContext = $normalizationContext;
+            if (isset($normalizationContext[AbstractNormalizer::ATTRIBUTES])) {
+                if ($inAttributes = isset($normalizationContext[AbstractNormalizer::ATTRIBUTES][$association])) {
+                    $childNormalizationContext[AbstractNormalizer::ATTRIBUTES] = $normalizationContext[AbstractNormalizer::ATTRIBUTES][$association];
+                }
+            } else {
+                $inAttributes = null;
+            }
+
+            if (
+                (null === $fetchEager = $propertyMetadata->getAttribute('fetch_eager'))
+                && (null !== $fetchEager = $propertyMetadata->getAttribute('fetchEager'))
+            ) {
+                @trigger_error('The "fetchEager" attribute is deprecated since 2.3. Please use "fetch_eager" instead.', \E_USER_DEPRECATED);
+            }
+
+            if (false === $fetchEager) {
+                continue;
+            }
+
+            if (true !== $fetchEager && (false === $propertyMetadata->isReadable() || false === $inAttributes)) {
+                continue;
+            }
+
+            // Avoid joining back to the parent that we just came from, but only on *ToOne relations
+            if (
+                null !== $parentAssociation
+                && isset($mapping['inversedBy'])
+                && $mapping['inversedBy'] === $parentAssociation
+                && $mapping['type'] & ClassMetadata::TO_ONE
+            ) {
+                continue;
+            }
+
+            $existingJoin = QueryBuilderHelper::getExistingJoin($queryBuilder, $parentAlias, $association);
+
+            if (null !== $existingJoin) {
+                $associationAlias = $existingJoin->getAlias();
+                $isLeftJoin = Join::LEFT_JOIN === $existingJoin->getJoinType();
+            } else {
+                $isNullable = $mapping['joinColumns'][0]['nullable'] ?? true;
+                $isLeftJoin = false !== $wasLeftJoin || true === $isNullable;
+                $method = $isLeftJoin ? 'leftJoin' : 'innerJoin';
+
+                $associationAlias = $queryNameGenerator->generateJoinAlias($association);
+                $queryBuilder->{$method}(sprintf('%s.%s', $parentAlias, $association), $associationAlias);
+                ++$joinCount;
+            }
+
+            if (true === $fetchPartial) {
+                try {
+                    throw new RuntimeException('Partial fetching is disabled in eCamp, to prevent lowering the code coverage due to a feature we don\'t use');
+                    //$this->addSelect($queryBuilder, $mapping['targetEntity'], $associationAlias, $options);
+                } catch (ResourceClassNotFoundException $resourceClassNotFoundException) {
+                    continue;
+                }
+            } else {
+                $this->addSelectOnce($queryBuilder, $associationAlias);
+            }
+
+            // Avoid recursive joins for self-referencing relations
+            if ($mapping['targetEntity'] === $resourceClass) {
+                continue;
+            }
+
+            // Only join the relation's relations recursively if it's a readableLink
+            if (true !== $fetchEager && (true !== $propertyMetadata->isReadableLink())) {
+                continue;
+            }
+
+            if (isset($attributesMetadata[$association])) {
+                $maxDepth = $attributesMetadata[$association]->getMaxDepth();
+
+                // The current depth is the lowest max depth available in the ancestor tree.
+                if (null !== $maxDepth && (null === $currentDepth || $maxDepth < $currentDepth)) {
+                    $currentDepth = $maxDepth;
+                }
+            }
+
+            $this->joinRelations($queryBuilder, $queryNameGenerator, $mapping['targetEntity'], $forceEager, $fetchPartial, $associationAlias, $options, $childNormalizationContext, $isLeftJoin, $joinCount, $currentDepth, $association);
+        }
+    }
+
+//    private function addSelect(QueryBuilder $queryBuilder, string $entity, string $associationAlias, array $propertyMetadataOptions) {
+//        $select = [];
+//        $entityManager = $queryBuilder->getEntityManager();
+//        $targetClassMetadata = $entityManager->getClassMetadata($entity);
+//        if (!empty($targetClassMetadata->subClasses)) {
+//            $this->addSelectOnce($queryBuilder, $associationAlias);
+//
+//            return;
+//        }
+//
+//        foreach ($this->propertyNameCollectionFactory->create($entity) as $property) {
+//            $propertyMetadata = $this->propertyMetadataFactory->create($entity, $property, $propertyMetadataOptions);
+//
+//            if (true === $propertyMetadata->isIdentifier()) {
+//                $select[] = $property;
+//
+//                continue;
+//            }
+//
+//            // If it's an embedded property see below
+//            if (!\array_key_exists($property, $targetClassMetadata->embeddedClasses)) {
+//                //the field test allows to add methods to a Resource which do not reflect real database fields
+//                if ($targetClassMetadata->hasField($property) && (true === $propertyMetadata->getAttribute('fetchable') || $propertyMetadata->isReadable())) {
+//                    $select[] = $property;
+//                }
+//
+//                continue;
+//            }
+//
+//            // It's an embedded property, select relevant subfields
+//            foreach ($this->propertyNameCollectionFactory->create($targetClassMetadata->embeddedClasses[$property]['class']) as $embeddedProperty) {
+//                $propertyMetadata = $this->propertyMetadataFactory->create($entity, $property, $propertyMetadataOptions);
+//                $propertyName = "{$property}.{$embeddedProperty}";
+//                if ($targetClassMetadata->hasField($propertyName) && (true === $propertyMetadata->getAttribute('fetchable') || $propertyMetadata->isReadable())) {
+//                    $select[] = $propertyName;
+//                }
+//            }
+//        }
+//
+//        $queryBuilder->addSelect(sprintf('partial %s.{%s}', $associationAlias, implode(',', $select)));
+//    }
+
+    private function addSelectOnce(QueryBuilder $queryBuilder, string $alias) {
+        $existingSelects = array_reduce($queryBuilder->getDQLPart('select') ?? [], function ($existing, $dqlSelect) {
+            return ($dqlSelect instanceof Select) ? array_merge($existing, $dqlSelect->getParts()) : $existing;
+        }, []);
+
+        if (!\in_array($alias, $existingSelects, true)) {
+            $queryBuilder->addSelect($alias);
+        }
+    }
+
+    /**
+     * Gets the serializer context.
+     *
+     * @param string $contextType normalization_context or denormalization_context
+     * @param array  $options     represents the operation name so that groups are the one of the specific operation
+     */
+    private function getNormalizationContext(string $resourceClass, string $contextType, array $options): array {
+        if (null !== $this->requestStack && null !== $this->serializerContextBuilder && null !== $request = $this->requestStack->getCurrentRequest()) {
+            return $this->serializerContextBuilder->createFromRequest($request, 'normalization_context' === $contextType);
+        }
+
+        $resourceMetadata = $this->resourceMetadataFactory->create($resourceClass);
+        if (isset($options['collection_operation_name'])) {
+            $context = $resourceMetadata->getCollectionOperationAttribute($options['collection_operation_name'], $contextType, null, true);
+        } elseif (isset($options['item_operation_name'])) {
+            $context = $resourceMetadata->getItemOperationAttribute($options['item_operation_name'], $contextType, null, true);
+        } else {
+            $context = $resourceMetadata->getAttribute($contextType);
+        }
+
+        return $context ?? [];
+    }
+}
diff --git a/api/src/Entity/Activity.php b/api/src/Entity/Activity.php
index 779b6cd56b..514ab047ab 100644
--- a/api/src/Entity/Activity.php
+++ b/api/src/Entity/Activity.php
@@ -10,6 +10,7 @@
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Validator\Constraints as Assert;
 
 /**
@@ -22,10 +23,12 @@
     itemOperations: [
         'get',
         'patch' => [
-            'validation_groups' => ['Default', 'activity:update'],
+            'validation_groups' => ['Default', 'update'],
         ],
         'delete',
     ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['camp'])]
 class Activity extends AbstractContentNodeOwner implements BelongsToCampInterface {
@@ -35,6 +38,7 @@ class Activity extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\OneToMany(targetEntity="ScheduleEntry", mappedBy="activity", orphanRemoval=true)
      */
     #[ApiProperty(writable: false, example: '["/schedule_entries/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $scheduleEntries;
 
     /**
@@ -53,6 +57,7 @@ class Activity extends AbstractContentNodeOwner implements BelongsToCampInterfac
      */
     #[Assert\DisableAutoMapping] // camp is set in the DataPersister
     #[ApiProperty(writable: false, example: '/camps/1a2b3c4d')]
+    #[Groups(['read'])]
     public ?Camp $camp = null;
 
     /**
@@ -63,7 +68,8 @@ class Activity extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\JoinColumn(nullable=false)
      */
     #[ApiProperty(example: '/categories/1a2b3c4d')]
-    #[AssertBelongsToSameCamp(groups: ['activity:update'])]
+    #[AssertBelongsToSameCamp(groups: ['update'])]
+    #[Groups(['read', 'write'])]
     public ?Category $category = null;
 
     /**
@@ -72,6 +78,7 @@ class Activity extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\Column(type="text")
      */
     #[ApiProperty(example: 'Sportolympiade')]
+    #[Groups(['read', 'write'])]
     public ?string $title = null;
 
     /**
@@ -80,6 +87,7 @@ class Activity extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\Column(type="text")
      */
     #[ApiProperty(example: 'Spielwiese')]
+    #[Groups(['read', 'write'])]
     public string $location = '';
 
     public function __construct() {
@@ -98,11 +106,24 @@ public function setRootContentNode(?ContentNode $rootContentNode) {
     }
 
     #[Assert\DisableAutoMapping]
+    #[Groups(['read'])]
     public function getRootContentNode(): ?ContentNode {
         // Getter is here to add annotations to parent class property
         return $this->rootContentNode;
     }
 
+    /**
+     * Overridden in order to add annotations.
+     *
+     * {@inheritdoc}
+     *
+     * @return ContentNode[]
+     */
+    #[Groups(['read'])]
+    public function getContentNodes(): array {
+        return parent::getContentNodes();
+    }
+
     /**
      * The list of people that are responsible for planning or carrying out this activity.
      *
diff --git a/api/src/Entity/ActivityResponsible.php b/api/src/Entity/ActivityResponsible.php
index 9d49abe9dd..a4238196aa 100644
--- a/api/src/Entity/ActivityResponsible.php
+++ b/api/src/Entity/ActivityResponsible.php
@@ -7,6 +7,7 @@
 use App\Validator\AssertBelongsToSameCamp;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
+use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Validator\Constraints as Assert;
 
 /**
@@ -20,6 +21,8 @@
 #[ApiResource(
     collectionOperations: ['get', 'post'],
     itemOperations: ['get', 'delete'],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[UniqueEntity(fields: ['activity', 'campCollaboration'])]
 class ActivityResponsible extends BaseEntity implements BelongsToCampInterface {
@@ -31,6 +34,7 @@ class ActivityResponsible extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\NotNull]
     #[ApiProperty(example: '/activities/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?Activity $activity = null;
 
     /**
@@ -41,6 +45,7 @@ class ActivityResponsible extends BaseEntity implements BelongsToCampInterface {
      */
     #[ApiProperty(example: '/camp_collaborations/1a2b3c4d')]
     #[AssertBelongsToSameCamp]
+    #[Groups(['read', 'write'])]
     public ?CampCollaboration $campCollaboration = null;
 
     #[ApiProperty(readable: false)]
diff --git a/api/src/Entity/BaseEntity.php b/api/src/Entity/BaseEntity.php
index c811ac8c4a..a77a5bc36b 100644
--- a/api/src/Entity/BaseEntity.php
+++ b/api/src/Entity/BaseEntity.php
@@ -7,6 +7,7 @@
 use DateTime;
 use Doctrine\ORM\Mapping as ORM;
 use Gedmo\Mapping\Annotation as Gedmo;
+use Symfony\Component\Serializer\Annotation\Groups;
 
 /**
  * @ORM\MappedSuperclass
@@ -25,6 +26,7 @@ abstract class BaseEntity {
      * @ORM\CustomIdGenerator(class=IdGenerator::class)
      */
     #[ApiProperty(writable: false, example: '1a2b3c4d')]
+    #[Groups(['read'])]
     protected string $id;
 
     /**
diff --git a/api/src/Entity/Camp.php b/api/src/Entity/Camp.php
index ca30302c84..1d3ee19140 100644
--- a/api/src/Entity/Camp.php
+++ b/api/src/Entity/Camp.php
@@ -25,26 +25,37 @@
         'post' => [
             'security' => 'is_fully_authenticated()',
             'input_formats' => ['jsonld', 'jsonapi', 'json'],
-            'validation_groups' => ['Default', 'camp:create'],
+            'validation_groups' => ['Default', 'create'],
+            'denormalization_context' => ['groups' => ['write', 'create']],
+            'normalization_context' => self::ITEM_NORMALIZATION_CONTEXT,
         ],
     ],
     itemOperations: [
-        'get' => ['security' => 'object.owner == user or is_granted("ROLE_ADMIN")'],
+        'get' => [
+            'security' => 'object.owner == user or is_granted("ROLE_ADMIN")',
+            'normalization_context' => self::ITEM_NORMALIZATION_CONTEXT,
+        ],
         'patch' => [
             'security' => 'object.owner == user or is_granted("ROLE_ADMIN")',
-            'denormalization_context' => [
-                'groups' => ['camp:update'],
-                'allow_extra_attributes' => false,
-            ],
+            'denormalization_context' => ['groups' => ['write', 'update']],
+            'normalization_context' => self::ITEM_NORMALIZATION_CONTEXT,
         ],
         'delete' => ['security' => 'object.owner == user or is_granted("ROLE_ADMIN")'],
-    ]
+    ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 class Camp extends BaseEntity implements BelongsToCampInterface {
+    public const ITEM_NORMALIZATION_CONTEXT = [
+        'groups' => ['read', 'Camp:Periods', 'Period:Days'],
+        'swagger_definition_name' => 'read',
+    ];
+
     /**
      * @ORM\OneToMany(targetEntity="CampCollaboration", mappedBy="camp", orphanRemoval=true)
      */
     #[SerializedName('campCollaborations')]
+    #[Groups(['read'])]
     public Collection $collaborations;
 
     /**
@@ -56,9 +67,12 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OrderBy({"start": "ASC"})
      */
     #[Assert\Valid]
-    #[Assert\Count(min: 1, groups: ['camp:create'])]
-    #[ApiProperty(writableLink: true, example: '[{ "description": "Hauptlager", "start": "2022-01-01", "end": "2022-01-08" }]')]
-    #[Groups(['Default'])]
+    #[Assert\Count(min: 1, groups: ['create'])]
+    #[ApiProperty(
+        writableLink: true,
+        example: '[{ "description": "Hauptlager", "start": "2022-01-01", "end": "2022-01-08" }]',
+    )]
+    #[Groups(['read', 'create'])]
     public Collection $periods;
 
     /**
@@ -67,6 +81,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="Category", mappedBy="camp", orphanRemoval=true)
      */
     #[ApiProperty(writable: false, example: '["/categories/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $categories;
 
     /**
@@ -76,6 +91,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="Activity", mappedBy="camp", orphanRemoval=true)
      */
     #[ApiProperty(writable: false, example: '["/activities/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $activities;
 
     /**
@@ -85,6 +101,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="MaterialList", mappedBy="camp", orphanRemoval=true)
      */
     #[ApiProperty(writable: false, example: '["/material_lists/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $materialLists;
 
     /**
@@ -104,7 +121,8 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\Type('bool')]
     #[Assert\DisableAutoMapping]
-    #[ApiProperty(example: false, writable: false)]
+    #[ApiProperty(example: true, writable: false)]
+    #[Groups(['read'])]
     public bool $isPrototype = false;
 
     /**
@@ -116,7 +134,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\NotBlank]
     #[ApiProperty(example: 'SoLa 2022')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public string $name;
 
     /**
@@ -129,7 +147,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[Assert\NotBlank]
     #[Assert\Length(max: 32)]
     #[ApiProperty(example: 'Abteilungs-Sommerlager 2022')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public string $title;
 
     /**
@@ -141,7 +159,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\Length(max: 128)]
     #[ApiProperty(example: 'Piraten')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $motto = null;
 
     /**
@@ -153,7 +171,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\Length(max: 128)]
     #[ApiProperty(example: 'Wiese hinter der alten Mühle')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $addressName = null;
 
     /**
@@ -165,7 +183,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\Length(max: 128)]
     #[ApiProperty(example: 'Schönriedweg 23')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $addressStreet = null;
 
     /**
@@ -177,7 +195,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\Length(max: 128)]
     #[ApiProperty(example: '1234')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $addressZipcode = null;
 
     /**
@@ -189,7 +207,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
     #[InputFilter\CleanHTML]
     #[Assert\Length(max: 128)]
     #[ApiProperty(example: 'Hintertüpfingen')]
-    #[Groups(['Default', 'camp:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $addressCity = null;
 
     /**
@@ -201,6 +219,7 @@ class Camp extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\DisableAutoMapping]
     #[ApiProperty(writable: false)]
+    #[Groups(['read'])]
     public ?User $creator = null;
 
     /**
@@ -222,6 +241,16 @@ public function __construct() {
         $this->materialLists = new ArrayCollection();
     }
 
+    /**
+     * @return Period[]
+     */
+    #[ApiProperty(readableLink: true)]
+    #[SerializedName('periods')]
+    #[Groups(['Camp:Periods'])]
+    public function getEmbeddedPeriods(): array {
+        return $this->periods->getValues();
+    }
+
     #[ApiProperty(readable: false)]
     public function getCamp(): ?Camp {
         return $this;
diff --git a/api/src/Entity/CampCollaboration.php b/api/src/Entity/CampCollaboration.php
index 53dc89cf1e..7a2566f4c4 100644
--- a/api/src/Entity/CampCollaboration.php
+++ b/api/src/Entity/CampCollaboration.php
@@ -26,8 +26,7 @@
         'get',
         'post' => [
             'denormalization_context' => [
-                'groups' => ['campCollaboration:create'],
-                'allow_extra_attributes' => false,
+                'groups' => ['write', 'create'],
             ],
             'openapi_context' => [
                 'description' => 'Also sends an invitation email to the inviteEmail address, if specified.',
@@ -36,13 +35,11 @@
     ],
     itemOperations: [
         'get',
-        'patch' => ['denormalization_context' => [
-            'groups' => ['campCollaboration:update'],
-            'allow_extra_attributes' => false,
-        ]],
+        'patch' => ['denormalization_context' => ['groups' => ['write', 'update']]],
         'delete',
     ],
-    normalizationContext: ['skip_null_values' => false],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['camp'])]
 class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
@@ -90,7 +87,7 @@ class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
      */
     #[AssertEitherIsNull(other: 'user')]
     #[ApiProperty(example: 'some-email@example.com')]
-    #[Groups(['Default', 'campCollaboration:create'])]
+    #[Groups(['read', 'create'])]
     public ?string $inviteEmail = null;
 
     /**
@@ -108,7 +105,7 @@ class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
      */
     #[AssertEitherIsNull(other: 'inviteEmail')]
     #[ApiProperty(example: '/users/1a2b3c4d')]
-    #[Groups(['Default', 'campCollaboration:create'])]
+    #[Groups(['read', 'create'])]
     public ?User $user = null;
 
     /**
@@ -118,7 +115,7 @@ class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
     #[ApiProperty(example: '/camps/1a2b3c4d')]
-    #[Groups(['Default', 'campCollaboration:create'])]
+    #[Groups(['read', 'create'])]
     public ?Camp $camp = null;
 
     /**
@@ -130,7 +127,7 @@ class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\Choice(choices: self::VALID_STATUS)]
     #[ApiProperty(default: self::STATUS_INVITED, example: self::STATUS_INACTIVE)]
-    #[Groups(['Default', 'campCollaboration:update'])]
+    #[Groups(['read', 'update'])]
     public string $status = self::STATUS_INVITED;
 
     /**
@@ -141,7 +138,7 @@ class CampCollaboration extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\Choice(choices: self::VALID_ROLES)]
     #[ApiProperty(example: self::ROLE_MEMBER)]
-    #[Groups(['Default', 'campCollaboration:create', 'campCollaboration:update'])]
+    #[Groups(['read', 'write'])]
     public string $role;
 
     /**
diff --git a/api/src/Entity/Category.php b/api/src/Entity/Category.php
index 422da4a670..6a85de82bc 100644
--- a/api/src/Entity/Category.php
+++ b/api/src/Entity/Category.php
@@ -21,15 +21,17 @@
  * @ORM\Entity
  */
 #[ApiResource(
-    collectionOperations: ['get', 'post'],
+    collectionOperations: [
+        'get',
+        'post' => ['denormalization_context' => ['groups' => ['write', 'create']]],
+    ],
     itemOperations: [
         'get',
-        'patch' => ['denormalization_context' => [
-            'groups' => ['category:update'],
-            'allow_extra_attributes' => false,
-        ]],
+        'patch' => ['denormalization_context' => ['groups' => ['write', 'update']]],
         'delete',
-    ]
+    ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['camp'])]
 class Category extends AbstractContentNodeOwner implements BelongsToCampInterface {
@@ -40,7 +42,7 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
     #[ApiProperty(example: '/camps/1a2b3c4d')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?Camp $camp = null;
 
     /**
@@ -53,7 +55,7 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * )
      */
     #[ApiProperty(example: '["/content_types/1a2b3c4d"]')]
-    #[Groups(['Default', 'category:update'])]
+    #[Groups(['read', 'write'])]
     public Collection $preferredContentTypes;
 
     /**
@@ -80,7 +82,7 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\Column(type="text", nullable=false)
      */
     #[ApiProperty(example: 'LS')]
-    #[Groups(['Default', 'category:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $short = null;
 
     /**
@@ -89,7 +91,7 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\Column(type="text", nullable=false)
      */
     #[ApiProperty(example: 'Lagersport')]
-    #[Groups(['Default', 'category:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $name = null;
 
     /**
@@ -99,7 +101,7 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      */
     #[Assert\Regex(pattern: '/^#[0-9a-zA-Z]{6}$/')]
     #[ApiProperty(example: '#4CAF50')]
-    #[Groups(['Default', 'category:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $color = null;
 
     /**
@@ -109,8 +111,8 @@ class Category extends AbstractContentNodeOwner implements BelongsToCampInterfac
      * @ORM\Column(type="string", length=1, nullable=false)
      */
     #[Assert\Choice(choices: ['a', 'A', 'i', 'I', '1'])]
-    #[ApiProperty(default: '1', example: 'a')]
-    #[Groups(['Default', 'category:update'])]
+    #[ApiProperty(default: '1', example: '1')]
+    #[Groups(['read', 'write'])]
     public string $numberingStyle = '1';
 
     public function __construct() {
@@ -159,11 +161,24 @@ public function setRootContentNode(?ContentNode $rootContentNode) {
     }
 
     #[Assert\DisableAutoMapping]
+    #[Groups(['read'])]
     public function getRootContentNode(): ?ContentNode {
         // Getter is here to add annotations to parent class property
         return $this->rootContentNode;
     }
 
+    /**
+     * Overridden in order to add annotations.
+     *
+     * {@inheritdoc}
+     *
+     * @return ContentNode[]
+     */
+    #[Groups(['read'])]
+    public function getContentNodes(): array {
+        return parent::getContentNodes();
+    }
+
     public function getStyledNumber(int $num): string {
         switch ($this->numberingStyle) {
             case 'a':
diff --git a/api/src/Entity/ContentNode.php b/api/src/Entity/ContentNode.php
index 92b0ffc645..510ee87d47 100644
--- a/api/src/Entity/ContentNode.php
+++ b/api/src/Entity/ContentNode.php
@@ -26,18 +26,20 @@
  * @ORM\Entity
  */
 #[ApiResource(
-    collectionOperations: ['get', 'post'],
+    collectionOperations: [
+        'get',
+        'post' => ['denormalization_context' => ['groups' => ['write', 'create']]],
+    ],
     itemOperations: [
         'get',
         'patch' => [
-            'denormalization_context' => [
-                'groups' => ['contentNode:update'],
-                'allow_extra_attributes' => false,
-            ],
-            'validation_groups' => ['Default', 'contentNode:update'],
+            'denormalization_context' => ['groups' => ['write', 'update']],
+            'validation_groups' => ['Default', 'update'],
         ],
         'delete' => ['security' => 'object.owner === null'],
-    ]
+    ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['parent'])]
 class ContentNode extends BaseEntity implements BelongsToCampInterface {
@@ -57,6 +59,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=true)
      */
     #[ApiProperty(writable: false, example: '/content_nodes/1a2b3c4d')]
+    #[Groups(['read'])]
     public ContentNode $root;
 
     /**
@@ -80,10 +83,10 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
         messageBothNull: 'Must not be null on non-root content nodes.',
         messageNoneNull: 'Must be null on root content nodes.'
     )]
-    #[AssertBelongsToSameOwner(groups: ['contentNode:update'])]
-    #[AssertNoLoop(groups: ['contentNode:update'])]
+    #[AssertBelongsToSameOwner(groups: ['update'])]
+    #[AssertNoLoop(groups: ['update'])]
     #[ApiProperty(example: '/content_nodes/1a2b3c4d')]
-    #[Groups(['Default', 'contentNode:update'])]
+    #[Groups(['read', 'write'])]
     public ?ContentNode $parent = null;
 
     /**
@@ -92,6 +95,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="ContentNode", mappedBy="parent", cascade={"remove"})
      */
     #[ApiProperty(writable: false, example: '["/content_nodes/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $children;
 
     /**
@@ -101,7 +105,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="text", nullable=true)
      */
     #[ApiProperty(example: 'footer')]
-    #[Groups(['Default', 'contentNode:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $slot = null;
 
     /**
@@ -111,7 +115,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="integer", nullable=true)
      */
     #[ApiProperty(example: '0')]
-    #[Groups(['Default', 'contentNode:update'])]
+    #[Groups(['read', 'write'])]
     public ?int $position = null;
 
     /**
@@ -122,7 +126,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="json", nullable=true)
      */
     #[ApiProperty(example: '{}')]
-    #[Groups(['Default', 'contentNode:update'])]
+    #[Groups(['read', 'write'])]
     public ?array $jsonConfig = null;
 
     /**
@@ -132,7 +136,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="text", nullable=true)
      */
     #[ApiProperty(example: 'Schlechtwetterprogramm')]
-    #[Groups(['Default', 'contentNode:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $instanceName = null;
 
     /**
@@ -144,7 +148,7 @@ class ContentNode extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=false)
      */
     #[ApiProperty(example: '/content_types/1a2b3c4d')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?ContentType $contentType = null;
 
     /**
@@ -165,6 +169,7 @@ public function __construct() {
      * The name of the content type of this content node. Read-only, for convenience.
      */
     #[ApiProperty(example: 'SafetyConcept')]
+    #[Groups(['read'])]
     public function getContentTypeName(): string {
         return $this->contentType?->name;
     }
@@ -174,6 +179,7 @@ public function getContentTypeName(): string {
      */
     #[SerializedName('owner')]
     #[ApiProperty(writable: false, example: '/activities/1a2b3c4d')]
+    #[Groups(['read'])]
     public function getRootOwner(): Activity | Category | AbstractContentNodeOwner {
         return $this->root->owner;
     }
@@ -185,6 +191,7 @@ public function getRootOwner(): Activity | Category | AbstractContentNodeOwner {
      * @throws Exception when the owner is neither an activity nor a category
      */
     #[ApiProperty(example: '/categories/1a2b3c4d')]
+    #[Groups(['read'])]
     public function getOwnerCategory(): Category {
         $owner = $this->getRootOwner();
 
diff --git a/api/src/Entity/ContentType.php b/api/src/Entity/ContentType.php
index ef7c242b35..bf64e2e80a 100644
--- a/api/src/Entity/ContentType.php
+++ b/api/src/Entity/ContentType.php
@@ -5,6 +5,7 @@
 use ApiPlatform\Core\Annotation\ApiProperty;
 use ApiPlatform\Core\Annotation\ApiResource;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Serializer\Annotation\Groups;
 
 /**
  * Defines a type of content that can be present in a content node tree. A content type
@@ -16,6 +17,7 @@
 #[ApiResource(
     collectionOperations: ['get'],
     itemOperations: ['get'],
+    normalizationContext: ['groups' => ['read']],
 )]
 class ContentType extends BaseEntity {
     /**
@@ -25,6 +27,7 @@ class ContentType extends BaseEntity {
      * @ORM\Column(type="string", length=32, unique=true)
      */
     #[ApiProperty(writable: false, example: 'SafetyConcept')]
+    #[Groups(['read'])]
     public ?string $name = null;
 
     /**
@@ -33,6 +36,7 @@ class ContentType extends BaseEntity {
      * @ORM\Column(type="boolean")
      */
     #[ApiProperty(writable: false, example: 'true')]
+    #[Groups(['read'])]
     public bool $active = true;
 
     /**
diff --git a/api/src/Entity/Day.php b/api/src/Entity/Day.php
index e8e8e1272c..ad68f99be3 100644
--- a/api/src/Entity/Day.php
+++ b/api/src/Entity/Day.php
@@ -10,6 +10,7 @@
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
+use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Serializer\Annotation\SerializedName;
 
 /**
@@ -26,6 +27,8 @@
 #[ApiResource(
     collectionOperations: ['get'],
     itemOperations: ['get'],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['period'])]
 #[UniqueEntity(fields: ['period', 'dayOffset'])]
@@ -36,6 +39,7 @@ class Day extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="DayResponsible", mappedBy="day", orphanRemoval=true)
      */
     #[ApiProperty(writable: false, example: '["/day_responsibles/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $dayResponsibles;
 
     /**
@@ -44,7 +48,8 @@ class Day extends BaseEntity implements BelongsToCampInterface {
      * @ORM\ManyToOne(targetEntity="Period", inversedBy="days")
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
-    #[ApiProperty(writable: false, example: '/periods/1a2b3c4d')]
+    #[ApiProperty(example: '/periods/1a2b3c4d')]
+    #[Groups(['read'])]
     public ?Period $period = null;
 
     /**
@@ -53,6 +58,7 @@ class Day extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="integer")
      */
     #[ApiProperty(writable: false, example: '1')]
+    #[Groups(['read'])]
     public int $dayOffset = 0;
 
     public function __construct() {
@@ -69,6 +75,7 @@ public function getCamp(): ?Camp {
      */
     #[ApiProperty(example: '2')]
     #[SerializedName('number')]
+    #[Groups(['read'])]
     public function getDayNumber(): int {
         return $this->dayOffset + 1;
     }
diff --git a/api/src/Entity/DayResponsible.php b/api/src/Entity/DayResponsible.php
index 4e770c96d2..8060fa4e03 100644
--- a/api/src/Entity/DayResponsible.php
+++ b/api/src/Entity/DayResponsible.php
@@ -27,6 +27,7 @@
 use App\Validator\AssertBelongsToSameCamp;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
+use Symfony\Component\Serializer\Annotation\Groups;
 use Symfony\Component\Validator\Constraints as Assert;
 
 /**
@@ -40,6 +41,8 @@
 #[ApiResource(
     collectionOperations: ['get', 'post'],
     itemOperations: ['get', 'delete'],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['day'])]
 #[UniqueEntity(fields: ['day', 'campCollaboration'])]
@@ -52,6 +55,7 @@ class DayResponsible extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\NotNull]
     #[ApiProperty(example: '/days/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?Day $day = null;
 
     /**
@@ -62,6 +66,7 @@ class DayResponsible extends BaseEntity implements BelongsToCampInterface {
      */
     #[AssertBelongsToSameCamp]
     #[ApiProperty(example: '/camp_collaborations/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?CampCollaboration $campCollaboration = null;
 
     #[ApiProperty(readable: false)]
diff --git a/api/src/Entity/MaterialItem.php b/api/src/Entity/MaterialItem.php
index c1397d2c95..fdc167e987 100644
--- a/api/src/Entity/MaterialItem.php
+++ b/api/src/Entity/MaterialItem.php
@@ -10,6 +10,7 @@
 use App\Validator\AssertEitherIsNull;
 use App\Validator\MaterialItemUpdateGroupSequence;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Component\Serializer\Annotation\Groups;
 
 /**
  * A physical item that is needed for carrying out a programme or camp.
@@ -22,7 +23,9 @@
         'get',
         'patch' => ['validation_groups' => MaterialItemUpdateGroupSequence::class],
         'delete',
-    ]
+    ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['materialList', 'period'])]
 class MaterialItem extends BaseEntity implements BelongsToCampInterface {
@@ -33,8 +36,9 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
      * @ORM\ManyToOne(targetEntity="MaterialList", inversedBy="materialItems")
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
-    #[AssertBelongsToSameCamp(compareToPrevious: true, groups: ['materialItem:update'])]
+    #[AssertBelongsToSameCamp(compareToPrevious: true, groups: ['update'])]
     #[ApiProperty(example: '/material_lists/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?MaterialList $materialList = null;
 
     /**
@@ -46,6 +50,7 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
     #[AssertBelongsToSameCamp]
     #[AssertEitherIsNull(other: 'contentNode')]
     #[ApiProperty(example: '/periods/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?Period $period = null;
 
     /**
@@ -57,6 +62,7 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
     #[AssertBelongsToSameCamp]
     #[AssertEitherisNull(other: 'period')]
     #[ApiProperty(example: '/content_nodes/1a2b3c4d')]
+    #[Groups(['read', 'write'])]
     public ?ContentNode $contentNode = null;
 
     /**
@@ -65,6 +71,7 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="text", nullable=false)
      */
     #[ApiProperty(example: 'Volleyball')]
+    #[Groups(['read', 'write'])]
     public ?string $article = null;
 
     /**
@@ -73,6 +80,7 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="float", nullable=true)
      */
     #[ApiProperty(example: 1.5)]
+    #[Groups(['read', 'write'])]
     public ?float $quantity = null;
 
     /**
@@ -81,6 +89,7 @@ class MaterialItem extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="text", nullable=true)
      */
     #[ApiProperty(example: 'kg')]
+    #[Groups(['read', 'write'])]
     public ?string $unit = null;
 
     #[ApiProperty(readable: false)]
diff --git a/api/src/Entity/MaterialList.php b/api/src/Entity/MaterialList.php
index f14991f423..a559bc403d 100644
--- a/api/src/Entity/MaterialList.php
+++ b/api/src/Entity/MaterialList.php
@@ -18,15 +18,13 @@
  * @ORM\Entity
  */
 #[ApiResource(
-    collectionOperations: ['get', 'post'],
-    itemOperations: [
+    collectionOperations: [
         'get',
-        'patch' => ['denormalization_context' => [
-            'groups' => ['materialList:update'],
-            'allow_extra_attributes' => false,
-        ]],
-        'delete',
-    ]
+        'post' => ['denormalization_context' => ['groups' => ['write', 'create']]],
+    ],
+    itemOperations: ['get', 'patch', 'delete'],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['camp'])]
 class MaterialList extends BaseEntity implements BelongsToCampInterface {
@@ -36,6 +34,7 @@ class MaterialList extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="MaterialItem", mappedBy="materialList")
      */
     #[ApiProperty(writable: false, example: '["/material_items/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $materialItems;
 
     /**
@@ -45,7 +44,7 @@ class MaterialList extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
     #[ApiProperty(example: '/camps/1a2b3c4d')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?Camp $camp = null;
 
     /**
@@ -63,7 +62,7 @@ class MaterialList extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="text", nullable=false)
      */
     #[ApiProperty(example: 'Lebensmittel')]
-    #[Groups(['Default', 'materialList:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $name = null;
 
     public function __construct() {
diff --git a/api/src/Entity/Period.php b/api/src/Entity/Period.php
index af38be88fd..7acd619fc8 100644
--- a/api/src/Entity/Period.php
+++ b/api/src/Entity/Period.php
@@ -11,6 +11,7 @@
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Component\Serializer\Annotation\Groups;
+use Symfony\Component\Serializer\Annotation\SerializedName;
 use Symfony\Component\Validator\Constraints as Assert;
 
 /**
@@ -20,25 +21,33 @@
  * @ORM\Entity
  */
 #[ApiResource(
-    collectionOperations: ['get', 'post'],
-    itemOperations: [
+    collectionOperations: [
         'get',
-        'patch' => ['denormalization_context' => [
-            'groups' => ['period:update'],
-            'allow_extra_attributes' => false,
-        ]],
+        'post' => ['denormalization_context' => ['groups' => ['write', 'create']]],
+    ],
+    itemOperations: [
+        'get' => ['normalization_context' => self::ITEM_NORMALIZATION_CONTEXT],
+        'patch',
         'delete',
-    ]
+    ],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['camp'])]
 class Period extends BaseEntity implements BelongsToCampInterface {
+    public const ITEM_NORMALIZATION_CONTEXT = [
+        'groups' => ['read', 'Period:Camp', 'Period:Days'],
+        'swagger_definition_name' => 'read',
+    ];
+
     /**
      * The days in this time period. These are generated automatically.
      *
      * @ORM\OneToMany(targetEntity="Day", mappedBy="period", orphanRemoval=true)
      * @ORM\OrderBy({"dayOffset": "ASC"})
      */
-    #[ApiProperty(writable: false, example: '["/days/1a2b3c4d"]')]
+    #[ApiProperty(writable: false, example: '["/days?period=/periods/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $days;
 
     /**
@@ -49,6 +58,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OrderBy({"periodOffset": "ASC"})
      */
     #[ApiProperty(writable: false, example: '["/schedule_entries/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $scheduleEntries;
 
     /**
@@ -58,6 +68,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      * @ORM\OneToMany(targetEntity="MaterialItem", mappedBy="period")
      */
     #[ApiProperty(writable: false, example: '["/material_items/1a2b3c4d"]')]
+    #[Groups(['read'])]
     public Collection $materialItems;
 
     /**
@@ -67,7 +78,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=false)
      */
     #[ApiProperty(example: '/camps/1a2b3c4d')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?Camp $camp = null;
 
     /**
@@ -79,7 +90,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\NotBlank]
     #[ApiProperty(example: 'Hauptlager')]
-    #[Groups(['Default', 'period:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $description = null;
 
     /**
@@ -95,7 +106,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\LessThanOrEqual(propertyPath: 'end')]
     #[ApiProperty(example: '2022-01-01', openapiContext: ['format' => 'date'])]
-    #[Groups(['Default', 'period:update'])]
+    #[Groups(['read', 'write'])]
     public ?DateTimeInterface $start = null;
 
     /**
@@ -106,7 +117,7 @@ class Period extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\GreaterThanOrEqual(propertyPath: 'start')]
     #[ApiProperty(example: '2022-01-08', openapiContext: ['format' => 'date'])]
-    #[Groups(['Default', 'period:update'])]
+    #[Groups(['read', 'write'])]
     public ?DateTimeInterface $end = null;
 
     public function __construct() {
@@ -115,6 +126,23 @@ public function __construct() {
         $this->materialItems = new ArrayCollection();
     }
 
+    /**
+     * @return Day[]
+     */
+    #[ApiProperty(readableLink: true)]
+    #[SerializedName('days')]
+    #[Groups('Period:Days')]
+    public function getEmbeddedDays(): array {
+        return $this->days->getValues();
+    }
+
+    #[ApiProperty(readableLink: true)]
+    #[SerializedName('camp')]
+    #[Groups(['Period:Camp'])]
+    public function getEmbeddedCamp(): ?Camp {
+        return $this->camp;
+    }
+
     public function getCamp(): ?Camp {
         return $this->camp;
     }
diff --git a/api/src/Entity/ScheduleEntry.php b/api/src/Entity/ScheduleEntry.php
index a274efae9d..cdbae6569c 100644
--- a/api/src/Entity/ScheduleEntry.php
+++ b/api/src/Entity/ScheduleEntry.php
@@ -20,15 +20,13 @@
  * @ORM\Entity
  */
 #[ApiResource(
-    collectionOperations: ['get', 'post'],
-    itemOperations: [
+    collectionOperations: [
         'get',
-        'patch' => ['denormalization_context' => [
-            'groups' => ['scheduleEntry:update'],
-            'allow_extra_attributes' => false,
-        ]],
-        'delete',
-    ]
+        'post' => ['denormalization_context' => ['groups' => ['write', 'create']]],
+    ],
+    itemOperations: ['get', 'patch', 'delete'],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 #[ApiFilter(SearchFilter::class, properties: ['period', 'activity'])]
 class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
@@ -40,7 +38,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      */
     #[AssertBelongsToSameCamp]
     #[ApiProperty(example: '/periods/1a2b3c4d')]
-    #[Groups(['Default', 'scheduleEntry:update'])]
+    #[Groups(['read', 'write'])]
     public ?Period $period = null;
 
     /**
@@ -52,7 +50,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      * @ORM\JoinColumn(nullable=false, onDelete="cascade")
      */
     #[ApiProperty(example: '/activities/1a2b3c4d')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?Activity $activity = null;
 
     /**
@@ -64,7 +62,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\GreaterThanOrEqual(value: 0)]
     #[ApiProperty(example: 1440)]
-    #[Groups(['Default', 'scheduleEntry:update'])]
+    #[Groups(['read', 'write'])]
     public int $periodOffset = 0;
 
     /**
@@ -74,7 +72,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      */
     #[Assert\GreaterThan(value: 0)]
     #[ApiProperty(example: 90)]
-    #[Groups(['Default', 'scheduleEntry:update'])]
+    #[Groups(['read', 'write'])]
     public int $length = 0;
 
     /**
@@ -88,7 +86,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      * --> left is a MariaDB keyword, therefore escaping for column name necessary
      */
     #[ApiProperty(default: 0, example: 0.6)]
-    #[Groups(['Default', 'scheduleEntry:update'])]
+    #[Groups(['read', 'write'])]
     public ?float $left = 0;
 
     /**
@@ -100,7 +98,7 @@ class ScheduleEntry extends BaseEntity implements BelongsToCampInterface {
      * @ORM\Column(type="float", nullable=true)
      */
     #[ApiProperty(example: 0.4)]
-    #[Groups(['Default', 'scheduleEntry:update'])]
+    #[Groups(['read', 'write'])]
     public ?float $width = 1;
 
     #[ApiProperty(readable: false)]
@@ -112,6 +110,7 @@ public function getCamp(): ?Camp {
      * The day on which this schedule entry starts.
      */
     #[ApiProperty(writable: false, example: '/days/1a2b3c4d')]
+    #[Groups(['read'])]
     public function getDay(): Day {
         $dayNumber = $this->getDayNumber();
 
@@ -129,6 +128,7 @@ public function getNumberingStyle(): ?string {
      * The day number of the day on which this schedule entry starts.
      */
     #[ApiProperty(example: '1')]
+    #[Groups(['read'])]
     public function getDayNumber(): int {
         return 1 + floor($this->periodOffset / (24 * 60));
     }
@@ -139,6 +139,7 @@ public function getDayNumber(): int {
      * second entry on a given day, its number will be 2.
      */
     #[ApiProperty(example: '2')]
+    #[Groups(['read'])]
     public function getScheduleEntryNumber(): int {
         $dayOffset = floor($this->periodOffset / (24 * 60)) * 24 * 60;
 
@@ -184,6 +185,7 @@ public function getScheduleEntryNumber(): int {
      * defined by the activity's category.
      */
     #[ApiProperty(example: '1.b')]
+    #[Groups(['read'])]
     public function getNumber(): string {
         $dayNumber = $this->getDayNumber();
         $scheduleEntryNumber = $this->getScheduleEntryNumber();
diff --git a/api/src/Entity/User.php b/api/src/Entity/User.php
index fc238c2382..e9661f9302 100644
--- a/api/src/Entity/User.php
+++ b/api/src/Entity/User.php
@@ -27,21 +27,19 @@
         'post' => [
             'security' => 'true', // allow unauthenticated clients to create (register) users
             'input_formats' => ['jsonld', 'jsonapi', 'json'],
-            'validation_groups' => ['Default', 'user:create'],
+            'validation_groups' => ['Default', 'create'],
+            'denormalization_context' => ['groups' => ['write', 'create']],
         ],
     ],
     itemOperations: [
         'get' => ['security' => 'is_granted("ROLE_ADMIN") or object == user'],
         'patch' => [
             'security' => 'is_granted("ROLE_ADMIN") or object == user',
-            'denormalization_context' => [
-                'groups' => 'user:update',
-                'allow_extra_attributes' => false,
-            ],
         ],
         'delete' => ['security' => 'is_granted("ROLE_ADMIN") and !object.ownsCamps()'],
     ],
-    denormalizationContext: ['groups' => ['Default']],
+    denormalizationContext: ['groups' => ['write']],
+    normalizationContext: ['groups' => ['read']],
 )]
 class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUserInterface {
     /**
@@ -69,7 +67,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[Assert\NotBlank]
     #[Assert\Email]
     #[ApiProperty(example: 'bi-pi@example.com')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $email = null;
 
     /**
@@ -81,7 +79,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[Assert\NotBlank]
     #[Assert\Regex(pattern: '/^[a-z0-9_.-]+$/')]
     #[ApiProperty(example: 'bipi')]
-    #[Groups(['Default'])]
+    #[Groups(['read', 'create'])]
     public ?string $username = null;
 
     /**
@@ -92,7 +90,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[InputFilter\Trim]
     #[InputFilter\CleanHTML]
     #[ApiProperty(example: 'Robert')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $firstname = null;
 
     /**
@@ -103,7 +101,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[InputFilter\Trim]
     #[InputFilter\CleanHTML]
     #[ApiProperty(example: 'Baden-Powell')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $surname = null;
 
     /**
@@ -114,7 +112,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[InputFilter\Trim]
     #[InputFilter\CleanHTML]
     #[ApiProperty(example: 'Bi-Pi')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $nickname = null;
 
     /**
@@ -125,7 +123,7 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
     #[InputFilter\Trim]
     #[Assert\Locale]
     #[ApiProperty(example: 'en')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $language = null;
 
     /**
@@ -149,10 +147,10 @@ class User extends BaseEntity implements UserInterface, PasswordAuthenticatedUse
      * A new password for this user. At least 8 characters.
      */
     #[SerializedName('password')]
-    #[Assert\NotBlank(groups: ['user:create'])]
+    #[Assert\NotBlank(groups: ['create'])]
     #[Assert\Length(min: 8)]
     #[ApiProperty(readable: false, writable: true, example: 'learning-by-doing-101')]
-    #[Groups(['Default', 'user:update'])]
+    #[Groups(['read', 'write'])]
     public ?string $plainPassword = null;
 
     public function __construct() {
@@ -166,6 +164,7 @@ public function __construct() {
      * @return null|string
      */
     #[ApiProperty(example: 'Robert Baden-Powell')]
+    #[Groups(['read'])]
     public function getDisplayName(): ?string {
         if (!empty($this->nickname)) {
             return $this->nickname;
diff --git a/api/src/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizer.php b/api/src/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizer.php
new file mode 100644
index 0000000000..ec7b35ca69
--- /dev/null
+++ b/api/src/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizer.php
@@ -0,0 +1,103 @@
+<?php
+
+namespace App\Serializer\Normalizer;
+
+use ApiPlatform\Core\Api\IriConverterInterface;
+use ApiPlatform\Core\Api\ResourceClassResolverInterface;
+use ApiPlatform\Core\DataProvider\ItemDataProviderInterface;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyMetadataFactoryInterface;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyNameCollectionFactoryInterface;
+use ApiPlatform\Core\Metadata\Resource\Factory\ResourceMetadataFactoryInterface;
+use ApiPlatform\Core\Security\ResourceAccessCheckerInterface;
+use ApiPlatform\Core\Serializer\AbstractItemNormalizer;
+use Symfony\Component\PropertyAccess\PropertyAccessorInterface;
+use Symfony\Component\Serializer\Exception\CircularReferenceException;
+use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactoryInterface;
+use Symfony\Component\Serializer\NameConverter\NameConverterInterface;
+use Symfony\Component\Serializer\Normalizer\AbstractNormalizer;
+use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
+use Symfony\Component\Serializer\SerializerAwareInterface;
+use Symfony\Component\Serializer\SerializerInterface;
+
+final class CircularReferenceDetectingHalItemNormalizer extends AbstractItemNormalizer implements NormalizerInterface, SerializerAwareInterface {
+    /**
+     * @internal
+     */
+    protected const HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS = 'hal_circular_reference_limit_counters';
+
+    public function __construct(private NormalizerInterface $decorated, PropertyNameCollectionFactoryInterface $propertyNameCollectionFactory, PropertyMetadataFactoryInterface $propertyMetadataFactory, IriConverterInterface $iriConverter, ResourceClassResolverInterface $resourceClassResolver, PropertyAccessorInterface $propertyAccessor = null, NameConverterInterface $nameConverter = null, ClassMetadataFactoryInterface $classMetadataFactory = null, ItemDataProviderInterface $itemDataProvider = null, bool $allowPlainIdentifiers = false, array $defaultContext = [], iterable $dataTransformers = [], ResourceMetadataFactoryInterface $resourceMetadataFactory = null, ResourceAccessCheckerInterface $resourceAccessChecker = null) {
+        $defaultContext[AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER] = function ($object) {
+            return ['_links' => ['self' => ['href' => $this->iriConverter->getIriFromItem($object)]]];
+        };
+        parent::__construct($propertyNameCollectionFactory, $propertyMetadataFactory, $iriConverter, $resourceClassResolver, $propertyAccessor, $nameConverter, $classMetadataFactory, $itemDataProvider, $allowPlainIdentifiers, $defaultContext, $dataTransformers, $resourceMetadataFactory, $resourceAccessChecker);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function supportsNormalization($data, $format = null): bool {
+        return $this->decorated->supportsNormalization($data, $format);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function normalize($object, $format = null, array $context = []) {
+        if ($this->isHalCircularReference($object, $context)) {
+            return $this->handleHalCircularReference($object, $format, $context);
+        }
+
+        return $this->decorated->normalize($object, $format, $context);
+    }
+
+    public function setSerializer(SerializerInterface $serializer) {
+        if ($this->decorated instanceof SerializerAwareInterface) {
+            $this->decorated->setSerializer($serializer);
+        }
+    }
+
+    /**
+     * Detects if the configured circular reference limit is reached.
+     *
+     * @throws CircularReferenceException
+     *
+     * @return bool
+     */
+    protected function isHalCircularReference(object $object, array &$context) {
+        $objectHash = spl_object_hash($object);
+
+        $circularReferenceLimit = $context[AbstractNormalizer::CIRCULAR_REFERENCE_LIMIT] ?? $this->defaultContext[AbstractNormalizer::CIRCULAR_REFERENCE_LIMIT];
+        if (isset($context[self::HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS][$objectHash])) {
+            if ($context[self::HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS][$objectHash] >= $circularReferenceLimit) {
+                unset($context[self::HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS][$objectHash]);
+
+                return true;
+            }
+
+            ++$context[self::HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS][$objectHash];
+        } else {
+            $context[self::HAL_CIRCULAR_REFERENCE_LIMIT_COUNTERS][$objectHash] = 1;
+        }
+
+        return false;
+    }
+
+    /**
+     * Handles a circular reference.
+     *
+     * If a circular reference handler is set, it will be called. Otherwise, a
+     * {@class CircularReferenceException} will be thrown.
+     *
+     * @final
+     *
+     * @throws CircularReferenceException
+     */
+    protected function handleHalCircularReference(object $object, string $format = null, array $context = []) {
+        $circularReferenceHandler = $context[AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER] ?? $this->defaultContext[AbstractNormalizer::CIRCULAR_REFERENCE_HANDLER];
+        if ($circularReferenceHandler) {
+            return $circularReferenceHandler($object, $format, $context);
+        }
+
+        throw new CircularReferenceException(sprintf('A circular reference has been detected when serializing the object of class "%s" (configured limit: %d).', get_debug_type($object), $context[AbstractNormalizer::CIRCULAR_REFERENCE_LIMIT] ?? $this->defaultContext[AbstractNormalizer::CIRCULAR_REFERENCE_LIMIT]));
+    }
+}
diff --git a/api/src/Serializer/Normalizer/RelatedCollectionLinkNormalizer.php b/api/src/Serializer/Normalizer/RelatedCollectionLinkNormalizer.php
index 09a170dd63..7d31ae54cc 100644
--- a/api/src/Serializer/Normalizer/RelatedCollectionLinkNormalizer.php
+++ b/api/src/Serializer/Normalizer/RelatedCollectionLinkNormalizer.php
@@ -115,7 +115,7 @@ public function getRelatedCollectionHref($object, $rel, array $context = []): st
         $resourceClass = $context['resource_class'] ?? get_class($object);
 
         if ($this->nameConverter instanceof AdvancedNameConverterInterface) {
-            $rel = $this->nameConverter->denormalize($rel, $resourceClass, null, $context);
+            $rel = $this->nameConverter->denormalize($rel, $resourceClass, null, array_merge($context, ['groups' => ['read']]));
         }
 
         try {
diff --git a/api/src/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactory.php b/api/src/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactory.php
new file mode 100644
index 0000000000..8a54d2f9f6
--- /dev/null
+++ b/api/src/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactory.php
@@ -0,0 +1,83 @@
+<?php
+
+/*
+ * This file is part of the API Platform project.
+ *
+ * (c) Kévin Dunglas <dunglas@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace App\Serializer;
+
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyMetadataFactoryInterface;
+use ApiPlatform\Core\Metadata\Property\PropertyMetadata;
+
+/**
+ * This is meant as a thin wrapper around
+ * ApiPlatform\Core\Metadata\Property\Factory\SerializerPropertyMetadataFactory.
+ * That class implements the automatic embedding logic based on serialization groups,
+ * described in https://api-platform.com/docs/core/serialization/#embedding-relations.
+ *
+ * However, we have our own system for serialization groups and embedding entities,
+ * with general groups 'read', 'write', 'create', 'update' etc. instead of entity-
+ * specific groups as they are used in the API platform docs ('book', 'book:update').
+ * Therefore, we don't want relations to be automatically embedded as soon as there
+ * is a property with a matching serialization group on the related entity.
+ *
+ * As an example, we don't want the author to be embedded in the book here:
+ *
+ * #[ApiResource(normalization_context: ['groups' => ['read']])]
+ * class Book {
+ *   #[Groups('read')]
+ *   public ?Person $author = null;
+ * }
+ *
+ * #[ApiResource(normalization_context: ['groups' => ['read']])]
+ * class Person {
+ *   #[Groups('read')]
+ *   public string $name = '';
+ * }
+ *
+ * To prevent the author from being embedded due to just the 'read' group, this
+ * class should be inserted just around SerializerPropertyMetadataFactory in the
+ * decorator chain. It will undo only the undesired changes to the property
+ * metadata that SerializerPropertyMetadataFactory adds.
+ *
+ * Currently, the SerializerPropertyMetadataFactory has a decoration priority of
+ * 30, so this class should be assigned a priority of 29.
+ * https://github.com/api-platform/core/blob/main/src/Bridge/Symfony/Bundle/Resources/config/metadata/metadata.xml#L65
+ */
+final class PreventAutomaticEmbeddingPropertyMetadataFactory implements PropertyMetadataFactoryInterface {
+    public function __construct(private PropertyMetadataFactoryInterface $decorated) {
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function create(string $resourceClass, string $property, array $options = []): PropertyMetadata {
+        $propertyMetadata = $this->decorated->create($resourceClass, $property, $options);
+
+        return new PropertyMetadata(
+            $propertyMetadata->getType(),
+            $propertyMetadata->getDescription(),
+            $propertyMetadata->isReadable(),
+            $propertyMetadata->isWritable(),
+            null, // reset readableLink to null
+            null, // reset writableLink to null
+            $propertyMetadata->isRequired(),
+            $propertyMetadata->isIdentifier(),
+            $propertyMetadata->getIri(),
+            $propertyMetadata->getChildInherited(),
+            $propertyMetadata->getAttributes(),
+            $propertyMetadata->getSubresource(),
+            $propertyMetadata->isInitializable(),
+            $propertyMetadata->getDefault(),
+            $propertyMetadata->getExample(),
+            $propertyMetadata->getSchema()
+        );
+    }
+}
diff --git a/api/src/Serializer/SerializerContextBuilder.php b/api/src/Serializer/SerializerContextBuilder.php
new file mode 100644
index 0000000000..c7a5e2a3b2
--- /dev/null
+++ b/api/src/Serializer/SerializerContextBuilder.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Serializer;
+
+use ApiPlatform\Core\Serializer\SerializerContextBuilderInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Adds some common settings to the normalization_context and denormalization_context, so that
+ * we don't have to repeat them everywhere.
+ *
+ * **NOTE**: The context that is set up here is ignored when building the OpenAPI documentation.
+ * This means that we shouldn't put any configuration in here that should be reflected in the
+ * API documentation. Settings such as skip_null_values and allow_extra_attributes are okay, but
+ * settings such as groups are not, because the groups need to be taken into account when
+ * building the payload schemas for the API documentation.
+ */
+final class SerializerContextBuilder implements SerializerContextBuilderInterface {
+    private SerializerContextBuilderInterface $decorated;
+
+    public function __construct(SerializerContextBuilderInterface $decorated) {
+        $this->decorated = $decorated;
+    }
+
+    public function createFromRequest(Request $request, bool $normalization, ?array $extractedAttributes = null): array {
+        $context = $this->decorated->createFromRequest($request, $normalization, $extractedAttributes);
+
+        if ($normalization) {
+            $context['skip_null_values'] = false;
+        }
+
+        if (!$normalization) {
+            $context['allow_extra_attributes'] = false;
+        }
+
+        return $context;
+    }
+}
diff --git a/api/src/Validator/MaterialItemUpdateGroupSequence.php b/api/src/Validator/MaterialItemUpdateGroupSequence.php
index 2e79219b47..916b61447b 100644
--- a/api/src/Validator/MaterialItemUpdateGroupSequence.php
+++ b/api/src/Validator/MaterialItemUpdateGroupSequence.php
@@ -7,6 +7,6 @@
 
 class MaterialItemUpdateGroupSequence implements ValidationGroupsGeneratorInterface {
     public function __invoke($object) {
-        return new GroupSequence(['materialItem:update', 'Default']); // now, no matter which is first in the class declaration, it will be tested in this order.
+        return new GroupSequence(['update', 'Default']); // now, no matter which is first in the class declaration, it will be tested in this order.
     }
 }
diff --git a/api/tests/Api/Activities/CreateActivityTest.php b/api/tests/Api/Activities/CreateActivityTest.php
index 78ad0ddcaa..b50ee2707c 100644
--- a/api/tests/Api/Activities/CreateActivityTest.php
+++ b/api/tests/Api/Activities/CreateActivityTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\Activities;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\Activity;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -67,6 +68,8 @@ public function testCreateActivityAllowsMissingLocation() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Activity::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge(['category' => $this->getIriFor('category1')], $attributes),
             [],
             $except
@@ -76,7 +79,13 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Activity::class,
-            $attributes,
+            OperationType::ITEM,
+            'get',
+            array_merge([
+                '_links' => [
+                    'contentNodes' => [],
+                ],
+            ], $attributes),
             ['category'],
             $except
         );
diff --git a/api/tests/Api/ActivityResponsibles/CreateActivityResponsibleTest.php b/api/tests/Api/ActivityResponsibles/CreateActivityResponsibleTest.php
index f2f7c8f1ef..403b4374a7 100644
--- a/api/tests/Api/ActivityResponsibles/CreateActivityResponsibleTest.php
+++ b/api/tests/Api/ActivityResponsibles/CreateActivityResponsibleTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\ActivityResponsibles;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\ActivityResponsible;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -68,6 +69,8 @@ public function testValidatesDuplicateActivityResponsible() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ActivityResponsible::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'activity' => $this->getIriFor('activity2'),
                 'campCollaboration' => $this->getIriFor('campCollaboration1'),
@@ -80,6 +83,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ActivityResponsible::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['activity', 'campCollaboration'],
             $except
diff --git a/api/tests/Api/CampCollaborations/CreateCampCollaborationTest.php b/api/tests/Api/CampCollaborations/CreateCampCollaborationTest.php
index acaee69c87..52a85945e1 100644
--- a/api/tests/Api/CampCollaborations/CreateCampCollaborationTest.php
+++ b/api/tests/Api/CampCollaborations/CreateCampCollaborationTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\CampCollaborations;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\CampCollaboration;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -123,6 +124,8 @@ public function testCreateCampCollaborationValidatesMissingRole() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             CampCollaboration::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'inviteEmail' => null,
                 'user' => $this->getIriFor('user1'),
@@ -136,6 +139,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             CampCollaboration::class,
+            OperationType::ITEM,
+            'get',
             array_merge([
                 '_links' => [
                     'user' => ['href' => $this->getIriFor('user1')],
diff --git a/api/tests/Api/Camps/CreateCampTest.php b/api/tests/Api/Camps/CreateCampTest.php
index 3ee10ceb8b..c4ad15496f 100644
--- a/api/tests/Api/Camps/CreateCampTest.php
+++ b/api/tests/Api/Camps/CreateCampTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\Camps;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\Camp;
 use App\Entity\User;
 use App\Tests\Api\ECampApiTestCase;
@@ -588,12 +589,14 @@ public function testCreateCampValidatesLongAddressCity() {
     }
 
     public function getExampleWritePayload($attributes = [], $except = []) {
-        return $this->getExamplePayload(Camp::class, $attributes, [], $except);
+        return $this->getExamplePayload(Camp::class, OperationType::COLLECTION, 'post', $attributes, [], $except);
     }
 
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Camp::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['periods'],
             $except
diff --git a/api/tests/Api/Categories/CreateCategoryTest.php b/api/tests/Api/Categories/CreateCategoryTest.php
index 60dac99264..4ecbf84ed2 100644
--- a/api/tests/Api/Categories/CreateCategoryTest.php
+++ b/api/tests/Api/Categories/CreateCategoryTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\Categories;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\Category;
 use App\Entity\ContentNode;
 use App\Tests\Api\ECampApiTestCase;
@@ -143,6 +144,8 @@ public function testCreateCategoryValidatesInvalidNumberingStyle() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Category::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'camp' => $this->getIriFor('camp1'),
                 'preferredContentTypes' => [$this->getIriFor('contentType1')],
@@ -155,6 +158,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Category::class,
+            OperationType::ITEM,
+            'get',
             array_merge([
                 '_links' => [
                     'contentNodes' => [],
diff --git a/api/tests/Api/ContentNodes/CreateContentNodeTest.php b/api/tests/Api/ContentNodes/CreateContentNodeTest.php
index 93ae150d0b..732f225889 100644
--- a/api/tests/Api/ContentNodes/CreateContentNodeTest.php
+++ b/api/tests/Api/ContentNodes/CreateContentNodeTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\ContentNodes;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\ContentNode;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -88,6 +89,8 @@ public function testCreateContentNodeValidatesMissingContentType() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ContentNode::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'parent' => $this->getIriFor('contentNode1'),
                 'contentType' => $this->getIriFor('contentTypeColumnLayout'),
@@ -100,6 +103,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ContentNode::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['parent', 'contentType'],
             $except
diff --git a/api/tests/Api/DayResponsibles/CreateDayResponsibleTest.php b/api/tests/Api/DayResponsibles/CreateDayResponsibleTest.php
index c6e267e36a..cbce3b1462 100644
--- a/api/tests/Api/DayResponsibles/CreateDayResponsibleTest.php
+++ b/api/tests/Api/DayResponsibles/CreateDayResponsibleTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\DayResponsibles;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\DayResponsible;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -68,6 +69,8 @@ public function testValidatesDuplicateDayResponsible() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             DayResponsible::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'day' => $this->getIriFor('day3period1'),
                 'campCollaboration' => $this->getIriFor('campCollaboration1'),
@@ -80,6 +83,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             DayResponsible::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['day', 'campCollaboration'],
             $except
diff --git a/api/tests/Api/ECampApiTestCase.php b/api/tests/Api/ECampApiTestCase.php
index e913c922dc..171fa8148b 100644
--- a/api/tests/Api/ECampApiTestCase.php
+++ b/api/tests/Api/ECampApiTestCase.php
@@ -110,10 +110,11 @@ protected function getEntityManager(): EntityManagerInterface {
         return $this->entityManager;
     }
 
-    protected function getExamplePayload(string $resourceClass, array $attributes = [], array $exceptExamples = [], array $exceptAttributes = []): array {
-        $shortName = $this->getResourceMetadataFactory()->create($resourceClass)->getShortName();
-        $schema = $this->getSchemaFactory()->buildSchema($resourceClass, 'json', Schema::TYPE_INPUT, 'POST');
-        $properties = ($schema->getDefinitions()[$shortName] ?? $schema->getDefinitions()[$shortName.'-Default'])['properties'];
+    protected function getExamplePayload(string $resourceClass, string $operationType, string $operationName, array $attributes = [], array $exceptExamples = [], array $exceptAttributes = []): array {
+        $schema = $this->getSchemaFactory()->buildSchema($resourceClass, 'json', 'get' === $operationName ? Schema::TYPE_OUTPUT : Schema::TYPE_INPUT, $operationType, $operationName);
+        preg_match('/\/([^\/]+)$/', $schema['$ref'], $matches);
+        $schemaName = $matches[1];
+        $properties = $schema->getDefinitions()[$schemaName]['properties'] ?? [];
         $writableProperties = array_filter($properties, fn ($property) => !($property['readOnly'] ?? false));
         $writablePropertiesWithExample = array_filter($writableProperties, fn ($property) => ($property['example'] ?? false));
         $examples = array_map(fn ($property) => $property['example'] ?? $property['default'] ?? null, $writablePropertiesWithExample);
diff --git a/api/tests/Api/MaterialItems/CreateMaterialItemTest.php b/api/tests/Api/MaterialItems/CreateMaterialItemTest.php
index 9d3bac1aff..a2c454c35c 100644
--- a/api/tests/Api/MaterialItems/CreateMaterialItemTest.php
+++ b/api/tests/Api/MaterialItems/CreateMaterialItemTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\MaterialItems;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\MaterialItem;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -164,6 +165,8 @@ public function testCreateMaterialItemAllowsMissingUnit() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             MaterialItem::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'materialList' => $this->getIriFor('materialList1'),
                 'period' => $this->getIriFor('period1'),
@@ -177,6 +180,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             MaterialItem::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['materialList', 'period', 'contentNode'],
             $except
diff --git a/api/tests/Api/MaterialLists/CreateMaterialListTest.php b/api/tests/Api/MaterialLists/CreateMaterialListTest.php
index c8a4be90e2..7fb2037935 100644
--- a/api/tests/Api/MaterialLists/CreateMaterialListTest.php
+++ b/api/tests/Api/MaterialLists/CreateMaterialListTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\MaterialLists;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\MaterialList;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -51,6 +52,8 @@ public function testCreateMaterialListValidatesMissingName() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             MaterialList::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge(['camp' => $this->getIriFor('camp1')], $attributes),
             [],
             $except
@@ -60,6 +63,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             MaterialList::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['camp'],
             $except
diff --git a/api/tests/Api/Periods/CreatePeriodTest.php b/api/tests/Api/Periods/CreatePeriodTest.php
index f03f7bd855..d91f6d0334 100644
--- a/api/tests/Api/Periods/CreatePeriodTest.php
+++ b/api/tests/Api/Periods/CreatePeriodTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\Periods;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\Period;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -150,6 +151,8 @@ public function testCreatePeriodValidatesStartAfterEnd() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Period::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge(['camp' => $this->getIriFor('camp1')], $attributes),
             [],
             $except
@@ -159,6 +162,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             Period::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['camp'],
             $except
diff --git a/api/tests/Api/ScheduleEntries/CreateScheduleEntryTest.php b/api/tests/Api/ScheduleEntries/CreateScheduleEntryTest.php
index 31c90828de..242c1cf803 100644
--- a/api/tests/Api/ScheduleEntries/CreateScheduleEntryTest.php
+++ b/api/tests/Api/ScheduleEntries/CreateScheduleEntryTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\ScheduleEntries;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\ScheduleEntry;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -141,6 +142,8 @@ public function testCreateScheduleEntryUsesDefaultForMissingWidth() {
     public function getExampleWritePayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ScheduleEntry::class,
+            OperationType::COLLECTION,
+            'post',
             array_merge([
                 'period' => $this->getIriFor('period1'),
                 'activity' => $this->getIriFor('activity1'),
@@ -153,6 +156,8 @@ public function getExampleWritePayload($attributes = [], $except = []) {
     public function getExampleReadPayload($attributes = [], $except = []) {
         return $this->getExamplePayload(
             ScheduleEntry::class,
+            OperationType::ITEM,
+            'get',
             $attributes,
             ['period', 'activity'],
             $except
diff --git a/api/tests/Api/Users/CreateUserTest.php b/api/tests/Api/Users/CreateUserTest.php
index a2ad02ffcc..3a57387ec8 100644
--- a/api/tests/Api/Users/CreateUserTest.php
+++ b/api/tests/Api/Users/CreateUserTest.php
@@ -2,6 +2,7 @@
 
 namespace App\Tests\Api\Users;
 
+use ApiPlatform\Core\Api\OperationType;
 use App\Entity\User;
 use App\Tests\Api\ECampApiTestCase;
 
@@ -393,10 +394,10 @@ public function testCreateUserValidatesBlankPassword() {
     }
 
     public function getExampleWritePayload($attributes = [], $except = []) {
-        return $this->getExamplePayload(User::class, $attributes, [], $except);
+        return $this->getExamplePayload(User::class, OperationType::COLLECTION, 'post', $attributes, [], $except);
     }
 
     public function getExampleReadPayload($attributes = [], $except = []) {
-        return $this->getExamplePayload(User::class, $attributes, [], $except);
+        return $this->getExamplePayload(User::class, OperationType::ITEM, 'get', $attributes, [], $except);
     }
 }
diff --git a/api/tests/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizerTest.php b/api/tests/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizerTest.php
new file mode 100644
index 0000000000..da8ffdfe56
--- /dev/null
+++ b/api/tests/Serializer/Normalizer/CircularReferenceDetectingHalItemNormalizerTest.php
@@ -0,0 +1,123 @@
+<?php
+
+namespace App\Tests\Serializer\Normalizer;
+
+use ApiPlatform\Core\Api\IriConverterInterface;
+use ApiPlatform\Core\Api\ResourceClassResolverInterface;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyMetadataFactoryInterface;
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyNameCollectionFactoryInterface;
+use App\Serializer\Normalizer\CircularReferenceDetectingHalItemNormalizer;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
+use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @internal
+ */
+class CircularReferenceDetectingHalItemNormalizerTest extends TestCase {
+    private CircularReferenceDetectingHalItemNormalizer $normalizer;
+
+    /**
+     * @var MockObject|NormalizerInterface
+     */
+    private $decoratedMock;
+
+    /**
+     * @var IriConverterInterface|MockObject
+     */
+    private $iriConverterMock;
+
+    protected function setUp(): void {
+        $this->decoratedMock = $this->createMock(ContextAwareNormalizerInterface::class);
+        $this->iriConverterMock = $this->createMock(IriConverterInterface::class);
+
+        $this->normalizer = new CircularReferenceDetectingHalItemNormalizer(
+            $this->decoratedMock,
+            $this->createMock(PropertyNameCollectionFactoryInterface::class),
+            $this->createMock(PropertyMetadataFactoryInterface::class),
+            $this->iriConverterMock,
+            $this->createMock(ResourceClassResolverInterface::class)
+        );
+
+        $this->normalizer->setSerializer($this->createMock(SerializerInterface::class));
+    }
+
+    public function testDelegatesSupportCheckToDecorated() {
+        $this->decoratedMock
+            ->expects($this->exactly(2))
+            ->method('supportsNormalization')
+            ->willReturnOnConsecutiveCalls(true, false)
+        ;
+
+        $this->assertTrue($this->normalizer->supportsNormalization([]));
+        $this->assertFalse($this->normalizer->supportsNormalization([]));
+    }
+
+    public function testDelegatesNormalizeToDecorated() {
+        // given
+        $resource = new Dummy();
+        $delegatedResult = [
+            'hello' => 'world',
+            '_links' => [
+                'items' => [['href' => '/children/1']],
+            ],
+        ];
+        $this->decoratedMock->expects($this->once())
+            ->method('normalize')
+            ->willReturn($delegatedResult)
+        ;
+
+        // when
+        $result = $this->normalizer->normalize($resource, null, []);
+
+        // then
+        $this->assertEquals($delegatedResult, $result);
+    }
+
+    public function testNormalizeDetectsCircularReference() {
+        // given
+        $normalizer = $this->normalizer;
+        $resource = new Dummy();
+        $related = new RelatedDummy();
+        $resource->related = $related;
+        $related->owner = $resource;
+
+        $this->decoratedMock
+            ->method('normalize')
+            ->willReturnCallback(function ($object, $format, $context) use ($normalizer) {
+                $result = ['serialized_id' => $object->id];
+                if ($object instanceof Dummy) {
+                    $result = array_merge($result, ['related' => $normalizer->normalize($object->related, $format, $context)]);
+                }
+                if ($object instanceof RelatedDummy) {
+                    $result = array_merge($result, ['owner' => $normalizer->normalize($object->owner, $format, $context)]);
+                }
+
+                return $result;
+            })
+        ;
+        $this->iriConverterMock
+            ->method('getIriFromItem')
+            ->willReturnCallback(fn ($object) => '/'.$object->id)
+        ;
+
+        // when
+        /** @var Dummy $result */
+        $result = $this->normalizer->normalize($resource, null, []);
+
+        // then
+        $this->assertEquals(['_links' => ['self' => ['href' => '/dummy']]], $result['related']['owner']);
+    }
+}
+
+class Dummy {
+    public string $id = 'dummy';
+    public ?RelatedDummy $related = null;
+}
+
+class RelatedDummy {
+    public string $id = 'related';
+    public ?Dummy $owner = null;
+}
diff --git a/api/tests/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactoryTest.php b/api/tests/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactoryTest.php
new file mode 100644
index 0000000000..9d0df4ce39
--- /dev/null
+++ b/api/tests/Serializer/PreventAutomaticEmbeddingPropertyMetadataFactoryTest.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace App\Tests\Serializer;
+
+use ApiPlatform\Core\Metadata\Property\Factory\PropertyMetadataFactoryInterface;
+use ApiPlatform\Core\Metadata\Property\PropertyMetadata;
+use ApiPlatform\Core\Metadata\Property\SubresourceMetadata;
+use App\Serializer\PreventAutomaticEmbeddingPropertyMetadataFactory;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\PropertyInfo\Type;
+
+/**
+ * @internal
+ */
+class PreventAutomaticEmbeddingPropertyMetadataFactoryTest extends TestCase {
+    public function testCreateResetsReadableLinkAndWritableLinkToNull() {
+        // given
+        $decorated = $this->createMock(PropertyMetadataFactoryInterface::class);
+        $propertyMetadata = new PropertyMetadata(
+            $this->createMock(Type::class),
+            'description',
+            true,
+            true,
+            true,
+            true,
+            true,
+            true,
+            '/iri/of/entity',
+            null,
+            [],
+            new SubresourceMetadata(Dummy::class, true, 3),
+            true,
+            null,
+            null,
+            []
+        );
+        $decorated->expects($this->once())
+            ->method('create')
+            ->willReturn($propertyMetadata)
+        ;
+        $factory = new PreventAutomaticEmbeddingPropertyMetadataFactory($decorated);
+
+        // when
+        $result = $factory->create(Dummy::class, 'myProperty', []);
+
+        // then
+        $this->assertEquals($propertyMetadata->getType(), $result->getType());
+        $this->assertEquals($propertyMetadata->getDescription(), $result->getDescription());
+        $this->assertEquals($propertyMetadata->isReadable(), $result->isReadable());
+        $this->assertEquals($propertyMetadata->isWritable(), $result->isWritable());
+        $this->assertEquals(null, $result->isReadableLink());
+        $this->assertEquals(null, $result->isWritableLink());
+        $this->assertEquals($propertyMetadata->isRequired(), $result->isRequired());
+        $this->assertEquals($propertyMetadata->isIdentifier(), $result->isIdentifier());
+        $this->assertEquals($propertyMetadata->getIri(), $result->getIri());
+        $this->assertEquals($propertyMetadata->getAttributes(), $result->getAttributes());
+        $this->assertEquals($propertyMetadata->getSubresource(), $result->getSubresource());
+        $this->assertEquals($propertyMetadata->isInitializable(), $result->isInitializable());
+        $this->assertEquals($propertyMetadata->getDefault(), $result->getDefault());
+        $this->assertEquals($propertyMetadata->getExample(), $result->getExample());
+        $this->assertEquals($propertyMetadata->getSchema(), $result->getSchema());
+    }
+}
+
+class Dummy {
+}
diff --git a/api/tests/Serializer/SerializerContextBuilderTest.php b/api/tests/Serializer/SerializerContextBuilderTest.php
new file mode 100644
index 0000000000..1d7a55c4c2
--- /dev/null
+++ b/api/tests/Serializer/SerializerContextBuilderTest.php
@@ -0,0 +1,79 @@
+<?php
+
+namespace App\Tests\Serializer;
+
+use ApiPlatform\Core\Serializer\SerializerContextBuilderInterface;
+use App\Serializer\SerializerContextBuilder;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * @internal
+ */
+class SerializerContextBuilderTest extends TestCase {
+    private SerializerContextBuilder $contextBuilder;
+
+    /**
+     * @var MockObject|SerializerContextBuilderInterface
+     */
+    private $decoratedMock;
+
+    protected function setUp(): void {
+        $this->decoratedMock = $this->createMock(SerializerContextBuilderInterface::class);
+
+        $this->contextBuilder = new SerializerContextBuilder($this->decoratedMock);
+    }
+
+    public function testAddsSkipNullValuesFalseWhenNormalizing() {
+        $request = $this->createMock(Request::class);
+        $this->decoratedMock
+            ->expects($this->exactly(1))
+            ->method('createFromRequest')
+            ->willReturn([])
+        ;
+
+        $result = $this->contextBuilder->createFromRequest($request, true);
+
+        $this->assertEquals(['skip_null_values' => false], $result);
+    }
+
+    public function testDoesntAddSkipNullValuesFalseWhenDenormalizing() {
+        $request = $this->createMock(Request::class);
+        $this->decoratedMock
+            ->expects($this->exactly(1))
+            ->method('createFromRequest')
+            ->willReturn([])
+        ;
+
+        $result = $this->contextBuilder->createFromRequest($request, false);
+
+        $this->assertNotEquals(['skip_null_values' => false], $result);
+    }
+
+    public function testDoesntAddAllowExtraAttributesFalseWhenNormalizing() {
+        $request = $this->createMock(Request::class);
+        $this->decoratedMock
+            ->expects($this->exactly(1))
+            ->method('createFromRequest')
+            ->willReturn([])
+        ;
+
+        $result = $this->contextBuilder->createFromRequest($request, true);
+
+        $this->assertNotEquals(['allow_extra_attributes' => false], $result);
+    }
+
+    public function testAddsAllowExtraAttributesFalseWhenDenormalizing() {
+        $request = $this->createMock(Request::class);
+        $this->decoratedMock
+            ->expects($this->exactly(1))
+            ->method('createFromRequest')
+            ->willReturn([])
+        ;
+
+        $result = $this->contextBuilder->createFromRequest($request, false);
+
+        $this->assertEquals(['allow_extra_attributes' => false], $result);
+    }
+}