Enhancement: User settings login field

We've introduced the new login field in the user settings,
where the admin can allow or disallow the login for the respective user.

https://github.com/owncloud/web/pull/8433
https://github.com/owncloud/web/pull/8799
https://github.com/owncloud/web/issues/8484
https://github.com/owncloud/web/issues/8467
https://github.com/owncloud/web/issues/8798
