audit user deletion
When a user closes their account in the webapp, let us confirm that all the things that are supposed to happen really happen:
- Can't login any more via webapp (CHECK)
- Can't login any more via Bitmask.
- User data is eventually purged.
- email sent to user account will bounce, with correct bounce message.
- client will not be able to send email with smtp client cert.
- username cannot be used again for registration (CHECK)
- can an admin reactivate the user account before it is purged?
(from redmine: created on 2015-04-21)