Implements synchronizing an external user's quota group with provided OAuth2 claim.
This functionality will allow system administrators to manage user's quota groups automatically.
Documentation is at forgejo/docs#1337
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8554
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: thezzisu <thezzisu@gmail.com>
Co-committed-by: thezzisu <thezzisu@gmail.com>
