IMHO providing Storage and Adapter should be something to look for in `Zend\Authentication` docs, we should leave things simple here. It is the same case about the `Module` class example I described in my other comment.

You can still leave the alias:
```PHP
           'invokables' => array(
                'my_auth_service' => 'Zend\Authentication\AuthenticationService',
            'alias' => array(
                'Zend\Authentication\AuthenticationService' => 'my_auth_service',
            ),
```