Add moderator notes capability to Appeals

[freiheit]

Pitch

Add ability for moderators to add private (only visible to other moderators) notes to appeals. Similar to the notes on reports.

Simple example: multi-person moderation team and one moderator is discussing the appeal with the user (whether via mastodon DMs, email, or elsewhere), so they want to leave a note like "Leave this appeal alone. I'm discussing this with the user".

Motivation

To help keep some kind of log of moderator activity within the Mastodon moderator interface somewhere, and to facilitate coordination between moderators on multi-moderator instances.

While a built-in mechanism for moderators to use the moderation interface for back-and-forth communication with the user about an appeal would be even better, I'm assuming that this is a much smaller and easier change to implement.

Cc: @ThisIsMissEm

[quintessence]

As an addendum for this: this would be an excellent use case for "Incident Report" / "Postmortem" style moderation reports, similar to what we see in the tech industry like:

https://postmortems.pagerduty.com/next_steps/

(Disclosure: I used to work for PagerDuty. That said, the doc is solid.)

There should be ways to flag a moderation report and/or appeal that is In Progress so that anyone on a distributed team knows that while they're catching up on all the chatter from when they were away. There should also be a way to create a higher level report with multiple sources (what if there are a bunch of reports that are about a single instance, and aren't user specific? etc.) so that aggregate trends can be found. (We currently do this manually and write reports as a private GitHub Wiki doc, but this is not ideal.)

[ThisIsMissEm]

I've actually been thinking about how to write up an "Incident Reports" feature, which is currently how several moderation teams I know of currently use report notes.

The idea here is that they write up a document that links together all the individual bits & pieces of reports relating to a single incident, linking everything together over time.

This deserves its own ticket but I haven't had a chance to research and write it up.

[quintessence]

What would you like to see in that ticket? I know I have thoughts on these as well (you know them) so I could probably do a write up.

[ThisIsMissEm]

The thing I'm mostly trying to figure out is how to make this buildable and not overtly complex.