Remove or adapt FAF Map upload OAuth login

[Brutus5000]

The FAF map upload feature requires a login to the FAF API.
For technical/security reasons the current OAuth client password flow will go out of service soon. This will effectively break the map upload here.

In order to fix this, the map editor needs to switch to a different OAuth library which supports PKCE flow. Our new OAuth service supports auto-discovery.

A new OAuth client id will be provided on request (some testing and configuration is implied on a client basis such as callback url and auth method via host or header). Contact me here or via FAF Zulip or FAF Discord.

If not possible as a last resort, remove the map upload feature again.