When a user use Authelia for the first time no device is enrolled in DB.
Now we test that the user does see the "not registered" message when
no device is enrolled and see the standard 2FA method when a device is
already enrolled.
A message is now displayed to the user when he first sign in
in Authelia letting him know that a device must be enrolled.
Also introduce a message letting him know when he is already
authenticated.
