[#4414] Update validation of IOT endpoint

Author: Viicos

src/openforms/registrations/api/filters.py

@@ -50,6 +50,13 @@ def validate(self, attrs: dict[str, Any]) -> dict[str, Any]:
                 )
             )
 
+        if registration_backend == "zgw-create-zaak" and "zgw_api_group" not in attrs:
+            raise serializers.ValidationError(
+                _(
+                    "'zgw_api_group' is required when 'registration_backend' is set to 'zgw-create-zaak'."
+                )
+            )
+
         return attrs
 
     def get_fields(self):

src/openforms/registrations/tests/test_views.py

@@ -150,6 +150,16 @@ def test_filter_with_invalid_zgw_group(self, m):
 
         self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
 
+    def test_missing_zgw_api_group(self, m):
+        user = StaffUserFactory.create()
+        url = furl(reverse("api:iotypen-list"))
+        url.args["registration_backend"] = "zgw-create-zaak"
+        self.client.force_login(user)
+
+        response = self.client.get(url.url)
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
     def test_missing_objects_api_group(self, m):
         user = StaffUserFactory.create()
         url = furl(reverse("api:iotypen-list"))