There is one special exception in here: the unread_user_ids column in
the message_conversations table had to be left as an integer array,
since the PostgreSQL intarray extension doesn't work with bigints. The
trigger that updates that column also needed a minor tweak.
This isn't good, but I don't really like how that was done anyway (it
was for the purpose of group messages that don't even exist), so it
could probably just be eliminated.
Deimos