Two assignments for same submission
Summary
Two tutors can have an active assignment for the same submission.
Steps to reproduce
Create two tutors with a subscription each (same type/key) and post the subscription pk to the assignment endpoint.
Example
What is the current bug behavior?
Two assignments will be created for the same submission.
What is the expected correct behavior?
Only one assignment should be created for every submission for every stage of the feedback.
Relevant logs and/or screenshots
See e2cf5bb3 for a testcase reproducing the bug.
Possible fixes
When the submissions in the Subscription model are filtered, those that have an assignment that is not done have to be filtered out.