Add ability to verify github account
Make it possible to validate the github account by going through the github login flow.
Do not allow users to connect using github.
When a user is verified (a record is present in the authmap table)
When the user is not verified (no record on the authmap table)
It's not possible the change the github id. if the github ID on the user profile is different than the one trying to login there is an error:
This is how you'd find that a user is validated:
$authmap = \Drupal::service('externalauth.authmap');
$linked = $authmap->get($user->id(), 'openid_connect.github_validation');
$validated = $linked !== FALSE;