public static function makeToken($launch) {
        global $CFG;
        if ( ! isset($launch->link->id) ) return false;
        $token = $CFG->wwwroot . '::' . $launch->link->id . '::';
        $token .= isset($launch->context->id) ? $launch->context->id : 'no_context';
        $token .= '::';
        $token .= isset($launch->user->id) ? $launch->context->id : 'no_user';
        return $token;
    }