Assignments: Improve submission history with attachments and submission timestamp

In both Sakai Grader and Classic Grader, the Previous submissions shows only inline text. The timestamp provided for the prior inline submissions is the timestamp that the instructor feedback was saved.

Classic Grader:

Sakai Grader:

What isn’t reflected in either of these histories is that in the 3:40:46 PM submission, my student added an attached file, then removed it when they resubmitted the most recent time. Also, the times listed for the prior submission is not the time the student submitted it, but the time the instructor graded it.

I believe for the history:

1. The timestamp for the prior submission should be the submission timestamp. This would add the history of inline submission timestamps to Sakai Grader (See my comments on SAK-49836)

2. Any attached files should be listed or linked, so there is some record of the files if the student removed the first attached file(s) when they resubmitted.