This PR has two parts:
* Add locking to goth and gothic calls with a RWMutex
The goth and gothic calls are currently unlocked and thus are a cause of multiple potential races
* Reattempt OAuth2 registration on login if registration failed
If OAuth2 registration fails at startup we currently disable the login_source however an alternative approach could be to reattempt registration on login attempt.
Fix#16096
Signed-off-by: Andrew Thornton <art27@cantab.net>
72738f0cb5