Problem: created resources OpenAPI schema is not specific enough

Solution: strongly type created resources as an array of strings

This patch changes the CreatedResource serializer to inherit from the RelatedField serializer. This lets the
OpenAPI schema generator know that created resources are URI strings.

closes: #4053
https://pulp.plan.io/issues/4053

pulpcore/pulpcore/app/serializers/task.py

@@ -9,7 +9,7 @@
 from .base import viewset_for_model
 
 
-class CreatedResourceSerializer(ModelSerializer):
+class CreatedResourceSerializer(RelatedField):
 
     def to_representation(self, data):
         # If the content object was deleted
@@ -79,7 +79,8 @@ class TaskSerializer(ModelSerializer):
     created_resources = CreatedResourceSerializer(
         help_text=_('Resources created by this task.'),
         many=True,
-        read_only=True
+        read_only=True,
+        view_name='None'  # This is a polymorphic field. The serializer does not need a view name.
     )
 
     class Meta: