RFC: Support annotations in the UI

[rien]

Note: this is an RFC with a suggested enhancement, it is not 100% we want this yet. More consideration is needed before starting implementation.

It would be useful to annotate certain elements of a report in order to come back to them later. For example: with programming exercises throughout the semester, one similar pair is often not enough to build a case. By flagging these submissions, teachers can go back to a report later to be reminded of what elements contributed to the suspicion.

How it would look like

I think we would like two types of annotations:

• Tags (e.g. suspicious, AI-generated, innocent, ...) that allow easy searching, flagging and grouping of submissions
  • Initially I think we could keep this per submissions. One could also tag a pair by tagging one (or both) submissions of that pair.
  • There should also be support for bulk tagging using the tables. This would allow tagging a whole cluster as "plagiarism" at once.
• Annotations on submissions. These would preferably support markdown to allow for proper formatting.
  • Annotating a whole submission
  • Annotating a specific line (or section) on a single submission
  • Annotating lines (or sections) in a pair of two submissions (e.g. "This function is copied")

In addition it would be useful to have an overview of all annotations with a quick link to the submission, pair or cluster.

Changes needed

This requires the annotations to be persistent in a way. As it might also be beneficial to also export these annotations elsewhere, we would need to expose this through some kind of interface.

• API endpoints need to be added (/reports/{id}/annotations and /reports/{id}/tags) to create, read and edit annotations.
• The UI needs to be updated to be able to add these annotations and send them to the API
• Specifically the annotations on pairs should be designed with care: showing this properly feels like a challenge
• The data tables should be able to search for tags, as well as search for, remove and bulk edit tags.
• These features should only be enabled when running in server mode (not when running standalone)

Related issue: #552