We've had the UploadReference table for some time now in core,
but it was added after ChatUpload was and chat was just never
moved over to this new system.
This commit changes all chat code dealing with uploads to create/
update/delete/query UploadReference records instead of ChatUpload
records for consistency. At a later date we will drop the ChatUpload
table, but for now keeping it for data backup.
The migration + post migration are the same, we need both in case
any chat uploads are added/removed during deploy.
Follow up to 766bcbc684
This fixes a gaffe from that commit where I passed in the
guardian to ChatMessageUpdater but then forgot to remove
the old way of setting the guardian and user instance variables
from the chat_message that was passed in.
Also, it moves the ensure_can_edit_message! check from the
controller into ChatMessageUpdater so all the access
checks are in the same place.
This commit adds last_editor_id to ChatMessage for parity with Post in
core, as well as adding user_id to the ChatMessageRevision record since
we need to know who is making edits and revisions to messages, in case
in future we want to allow more than just the current user to edit chat
messages. The backfill for data here simply uses the record's creating
user ID, but in future if we allow other people to edit the messages it
will use their ID.
