Fix relation between MultipleChoiceOption and FeedbackOption

When a MultipleChoiceOption is created via the API call PUT /mult-choice, a new FeedbackOption is now automatically inserted into the database that links to the same problem as the MultipleChoiceOption.

The response of PUT /mult-choice will now contain an mc_id that shows the ID of the new MultipleChoiceQuestion and a feedback_id with the ID of the new FeedbackOption.

The relation between MultipleChoiceOption and Problem is now removed. A new relation from FeedbackOption to MultipleChoiceOption is created. However, it is still possible to use problem.mc_options with a hybrid attribute that essentially runs a query in the background.

TODO:

• Ensure that if a FeedbackOption is deleted, the related MultipleChoiceOption is also deleted.

Closes #35 (closed) and #36 (closed).

zesje/api/feedback.py

@@ -141,6 +141,10 @@ class Feedback(Resource):
 
         # Delete mc_options associated with this feedback option
         if fb.mc_option:
+            if fb.problem.exam.finalized:
+                return dict(status=401, message='Cannot delete feedback option'
+                                                + ' attached to a multiple choice option in a finalized exam.'), 401
+
             db.session.delete(fb.mc_option)
             db.session.commit()