protected function createAuthCode()
 {
     $auth_codes_model = new waApiAuthCodesModel();
     $code = md5(microtime(true) . uniqid());
     // + 5 min
     $expires = date('Y-m-d H:i:s', time() + 300);
     $auth_codes_model->insert(array('code' => $code, 'client_id' => $this->client_id, 'contact_id' => $this->contact_id, 'scope' => waRequest::get('scope'), 'expires' => $expires));
     return $code;
 }