public function getAuthorizationCodeURL(){
        $parameters = array(
           'client_id' => $this->getClientID(),
           'scope' => $this->getScope(),
           'redirect_uri' => $this->getRedirectURL(),
           'response_type' => 'code',
           'state' => $this->getState()
       );
       $authorizationRequestUrl = CoreConstants::OAUTH2_AUTHORIZATION_REQUEST_URL;
       $authorizationRequestUrl .= '?' . http_build_query($parameters, null, '&', PHP_QUERY_RFC1738);
       return $authorizationRequestUrl;
    }