🐛 [#5089] Preventing case changes in 'service fetch config' api calls

Make sure that `body` and `query_params` on service fetch configuration keep their original case type.

In most cases we want to change the text case types of content, because the frontend and backend expect different case notations. For the service fetch `body` and `query_params` the case type schouldn't change, because this results in logic not being performed.

Backport-Of: #5089

src/openforms/variables/api/renderers.py

@@ -0,0 +1,12 @@
+from djangorestframework_camel_case.render import CamelCaseJSONRenderer
+
+
+class ServiceFetchConfigurationRenderer(CamelCaseJSONRenderer):
+    # The field body and query_params needs to be ignored, to prevent accidental snake_case to camelCase changes.
+    # See github issue https://github.com/open-formulieren/open-forms/issues/5089
+    json_underscoreize = {
+        "ignore_fields": (
+            "body",
+            "query_params",
+        )
+    }

src/openforms/variables/api/viewsets.py

@@ -8,6 +8,7 @@
 from openforms.forms.api.permissions import FormAPIPermissions
 
 from ..models import ServiceFetchConfiguration
+from .renderers import ServiceFetchConfigurationRenderer
 from .serializers import ServiceFetchConfigurationSerializer
 
 
@@ -26,6 +27,7 @@ class ServiceFetchConfigurationViewSet(viewsets.ReadOnlyModelViewSet):
     authentication_classes = (authentication.SessionAuthentication,)
     permission_classes = (FormAPIPermissions,)
     serializer_class = ServiceFetchConfigurationSerializer
+    renderer_classes = (ServiceFetchConfigurationRenderer,)
 
     queryset = ServiceFetchConfiguration.objects.order_by("service", "-pk")
     pagination_class = pagination.PageNumberPagination

src/openforms/variables/tests/test_viewsets.py

@@ -1,3 +1,5 @@
+import json
+
 from rest_framework import status
 from rest_framework.reverse import reverse
 from rest_framework.test import APITestCase
@@ -92,3 +94,43 @@ def test_service_fetch_configuration_have_the_right_properties(self):
         }
 
         self.assertEqual(response.data["results"][0], expected)
+
+    def test_service_fetch_configuration_list_returns_data_using_correct_text_case(
+        self,
+    ):
+        config = ServiceFetchConfigurationFactory.create(
+            name="Service fetch configuration 1",
+            method=ServiceFetchMethods.post,
+            query_params={
+                "snake_case": ["snake_case_data"],
+                "camelCase": ["camelCaseData"],
+            },
+            body={"snake_case": "snake_case_data", "camelCase": "camelCaseData"},
+        )
+        endpoint = reverse("api:servicefetchconfiguration-list")
+        self.client.force_authenticate(user=self.admin_user)
+
+        response = self.client.get(endpoint, format="json")
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        self.assertEqual(response.data["count"], 1)
+
+        content = json.loads(response.content)
+        expected = {
+            "id": config.pk,
+            "name": "Service fetch configuration 1",
+            "service": f"http://testserver{reverse('api:service-detail', kwargs={'pk': config.service.pk})}",
+            "path": "",
+            "method": ServiceFetchMethods.post.value,
+            "headers": {},
+            "queryParams": {
+                "snake_case": ["snake_case_data"],
+                "camelCase": ["camelCaseData"],
+            },
+            "body": {"snake_case": "snake_case_data", "camelCase": "camelCaseData"},
+            "dataMappingType": "",
+            "mappingExpression": None,
+            "cacheTimeout": None,
+        }
+
+        self.assertEqual(content["results"][0], expected)