title: Custom login password check with Laravel 5.4
body: <p>If a user tries to log into my Laravel application and the password won't match with the "password" column in the database, I want to check it against another password column ("old_system_password") too.</p>
  
  <p>I'm using the default Laravel authentication system, and as far as I understand I should be able to create a new "AuthController" and override the built in authentication methods. But I don't find any methods dealing with password matching in the vendor folder, and neither do I know how to tell Laravel to use my method instead of the default.</p>
  
  <p>I've searched the web for this, but any solutions I find seems to be only for older versions of Laravel.</p>
  
  <p>Any ideas?</p>