More back-end checks for merging copies
The following discussion from !380 (merged) should be addressed:
-
@Hugo started a discussion: This MR exactly mimicks the old front-end checks. While writing the tests, I realized we only warn the user whether we will modify the newly merged submission.
However, when transferring a copy from submission A to B, submission A will be modified and thus ungraded, but it won't trigger any warning. IMO we should catch this as well and warn the user.
We could either fix it in this MR, or make a new issue for it.