Admin "repair" mode

[anbraten]

As the current migration of #4762 will only fix user org names, I am thinking of a global repair api endpoint that could do some additional tasks like:

• updating user names from forge
• org names from forge
• checking each user has an user org
• updating user permissions
• doing repo repairs

[jenrik]

Consider giving users the option to run individual repair tasks. I'm concerned about the side-effect of running everything on large installations, e.g. rate-limits and general resource consumption