public static function getAuthSubTokenUri($next, $scope, $secure=0, $session=0,
                                               $request_uri = self::AUTHSUB_REQUEST_URI)
     {
         $querystring = '?next=' . urlencode($next)
             . '&scope=' . urldecode($scope)
             . '&secure=' . urlencode($secure)
             . '&session=' . urlencode($session);
         return $request_uri . $querystring;
     }