Temporary users already created on beta use the old format for their names (starting with *).
They should be renamed to use the new format (starting with ~, see parent task for more details).
To do:
- Send a general email to notify all developers. (This isn't like a production account rename, so we needn't try to warn specific temporary account owners who still have access to their accounts)
- Run a rename script on all beta sites with temporary accounts enabled, specifically to rename temporary accounts. (See subtask, which blocks this)