Resolve "Frontend for Models"

Closes #1 (closed)

aleksis/apps/lesrooster/schema/__init__.py

@@ -34,7 +34,8 @@ class Query(graphene.ObjectType):
 
     @staticmethod
     def resolve_slots(root, info):
-        return Slot.objects.all()
+        # FIXME: This does also return `Break` objects (but with type set to Slot)
+        return Slot.objects.non_polymorphic()
 
     @staticmethod
     def resolve_validity_ranges(root, info):