Draft: Improve user deletion consistency

An attempt to ensure something like #1415 (closed) does not happen or is at least debuggable.

• Deactivate the user before deletion to ensure no new posts/follows can be made during it
• Run the deletion in a transaction. This should reduce performance impact of a deletion since it will only use a single connection. Also makes sure an account cannot get stuck in a weird state between deleted and active. Made it possible to disable though, in case someone hits the issue mentioned above.
• Log more errors