feat: return schedule dry-runs with a separate status code

Schedule dry-runs returned a 201 response before, because the only check
for a 201 return code was, that the payload must not contain the
"projected" keyword.

As dry-runs don’t create any data 201 is not an appropriate status code.

program/views.py

@@ -372,6 +372,10 @@ class APIScheduleViewSet(
         # Otherwise try to resolve
         resolution = Schedule.resolve_conflicts(request.data, pk, show_pk)
 
+        if all(key in resolution for key in ["create", "update", "delete"]):
+            # this is a dry-run
+            return Response(resolution, status=status.HTTP_202_ACCEPTED)
+
         # If resolution went well
         if "projected" not in resolution:
             return Response(resolution, status=status.HTTP_201_CREATED)