[BC break] Added implements \Stringable to Translation Value Object (#344)

For more details see #344

Breaking changes:

Any class extending `\Ibexa\Contracts\Core\Repository\Values\Translation` will need to implement `\Stringable`.

Author: alongosz

phpstan-baseline.neon

@@ -8480,11 +8480,6 @@ parameters:
 			count: 1
 			path: src/lib/Base/Exceptions/UnauthorizedException.php
 
-		-
-			message: "#^Cannot cast Ibexa\\\\Contracts\\\\Core\\\\Repository\\\\Values\\\\Translation to string\\.$#"
-			count: 1
-			path: src/lib/Base/Exceptions/UserPasswordValidationException.php
-
 		-
 			message: "#^Method Ibexa\\\\Core\\\\Base\\\\Exceptions\\\\UserPasswordValidationException\\:\\:__construct\\(\\) has parameter \\$errors with no value type specified in iterable type array\\.$#"
 			count: 1
@@ -42900,11 +42895,6 @@ parameters:
 			count: 1
 			path: tests/lib/FieldType/FloatValueValidatorTest.php
 
-		-
-			message: "#^Cannot cast Ibexa\\\\Contracts\\\\Core\\\\Repository\\\\Values\\\\Translation to string\\.$#"
-			count: 1
-			path: tests/lib/FieldType/Generic/GenericTest.php
-
 		-
 			message: "#^Class Symfony\\\\Component\\\\Validator\\\\ConstraintViolation constructor invoked with 1 parameter, 6\\-10 required\\.$#"
 			count: 1

src/contracts/Repository/Values/Translation.php

@@ -8,12 +8,15 @@
 
 namespace Ibexa\Contracts\Core\Repository\Values;
 
+use Stringable;
+
 /**
- * Base class fro translation messages.
+ * Abstract for UI translation messages, use its extensions: Translation\Message, Translation\Plural.
  *
- * Use its extensions: Translation\Singular, Translation\Plural.
+ * @see \Ibexa\Contracts\Core\Repository\Values\Translation\Message
+ * @see \Ibexa\Contracts\Core\Repository\Values\Translation\Plural
  */
-abstract class Translation extends ValueObject
+abstract class Translation extends ValueObject implements Stringable
 {
 }