Use Query statements in Gatekeeper UserProvider

Possibility to parse additional query statements to UserProvider when instantiate new Gatekeeper

Eg:

// User Provider

$userProvider = new UserProvider('\app\models\User', function($query)
{
    $query->where('my_custom_field', '=', 'my_custom_value');
});

// Gatekeeper

$gatekeeper = new Gatekeeper($request, $response, $session, $userProvider);


// Other stuffs

.....