Remove unfinished Assignments from Tutors/Reviewers

Description / Overview

Provide a way to either remove unfinished assignments on a per user basis or for all users via one post.

Use cases

Some user forgot about a subscription with active assignments and is not reachable. Or worse, the UI is buggy and an assignment exists for a tutor but he has no way of working on it. In these cases there must be an easy way for a reviewer to remove unfinished assignments so others can continue the correcting process.

Links / references

Feature checklist

Backend

• either subscription or assignments (i'd prefer subscriptions) must be deletable by a reviewer user (for this probably an own implemenetation of the delete method on the view is necessary since we can't change the queryset to include all)

Frontend

• active subscriptions should be displayed next to tutors with the option to remove them