[Rubrics] Retain data when rubric is disconnected from assignment

[milesl]

If an instructor links a rubric to an assignment, enters data in the rubric in the speedgrader, and then un-links the rubric from that assignment, all data entered in the rubric will permanently lost without warning.

Re-linking the original rubric to the assignment will not restore any data that was previously entered into the rubric.

Please add either:

1. Automatic restoration of rubric data if a rubric is un-linked and then re-linked (the same way that grading data is retained even if a student enrollment is deleted)

2. A warning message displayed when attempting to unlink a rubric that will result in data loss

We had an instructor review* a quiz using a rubric: 200 students * 6 questions = 1200 manually graded questions. The instructor was testing various things, and un-linked the rubric. When they re-linked the rubric, they learned that all the previously-entered data was deleted without warning.

*I say "review" because you cannot grade a quiz with a rubric. The instructor was aware of this, and intended to copy the rubric values to the corresponding questions to finalize the grades.

[chriscas]

We just ran in to this issue yesterday.  Very disappointing that a ton of feedback can just vanish without warning with one accidental click.  At a minimum there should be a warning that pops up before removing a rubric if it's already been used in SpeedGrader.  Ideally, if a rubric is re-attached, the comments should come back with it (just like if a student is removed from a course and later re-added, all of their grades are restored).

I feel this is really a big and will try to escalate the issue through our CSM.

-Chris