This has backwards-compatibility-breaking changes to the formatters
of staff reply edits/deletions, which now only receive the
thread message for the edit/deletion with the original data in
the thread message's metadata.
Format-specific parts of replies, including the role name and
attachments, are now stored in separate columns. This allows us to
store only one version of the actual message body and, by keeping
format-specific data separate, reproduce formatter results regardless
of when they are called. This cleans up code around message formats
significantly and was required to support !edit/!delete properly.
Dragory