Add after_authentication Warden callback after signing in

We encountered a problem where we wanted to execute a proc after user login to assign cookies to a user, and we were going to do that by adding a callback to warden's after_authentication call. However, during 2FA, this gem initially logs the user out and then logs him or her back in when the user inputs the token code. The second time the user is supposed to log in, the callback is not ran because we use sign_in and not warden_authenticate. So I'm adding this manually call to the callback to make sure that those proc's are run.