Moderator Role

[Arcadius2006]

As an inbetween for Admin and Curator, the Moderator role would be able to delete most content and issue out warnings to users if needed, while not having full access to the server like Admins do

[Toastbrot236]

Since this issue in particular already exists and I don't need to open a new one anymore, I'll just dump how I'm intending to implement this here:

• Add the actual role to GameUserRole and allow most already existing admin API endpoints to be callable by it
• Implement #565. I already have this and the previous point implemented in a branch, but I ultimately decided against opening a PR with it because it'd be way too large (1100 additional lines). I'm splitting it into 3 sequential PRs (role, log and log tests).
• For the previous point, events should no longer be deleted when deleting their object, as otherwise there wouldn't be any way to track content deletions (especially deletions done by staff). Both moderation events and all events for deleted objects would be private, only visible to the actor, the object's publisher/owner, and any staff member. They would also have to be automatically deleted after some time.
• Also send notifications on moderation actions
• Add more admin API endpoints for moderation (e.g. playlist moderation, and #472)
• As usual, add some unit tests for most of the backend points
• Implement a level edit, user edit, and a mod/admin panel page for the refresh-web rewrite