/**
     * returns user object from standard parameter from request
     *
     * @return string
     */
    protected function getUserFromParameter(Pap_Contexts_Click $context) {
        $parameterName = Pap_Tracking_Request::getAffiliateClickParamName();
        if($parameterName == '') {
            $context->debug("  Cannot get name of request parameter for affiliate ID");
            return null;
        }
         
        $context->debug("  Trying to get affiliate from request parameter '$parameterName'");

        $userId = $context->getAffiliateId();
        if($userId != '') {
            $context->debug("    Setting affiliate from request parameter. Affiliate Id: ".$userId);
            return $this->getUserById($context, $userId);
        }

        $context->debug("    Affiliate not found in parameter");
        return null;
    }