/**
  * Returns all set custom parameters as JSON string
  *
  * @return string
  */
 protected function getJsonForResponse()
 {
     $json = ['eventType' => 'Cron', 'appName' => $this->config->getNewRelicAppName(), 'appId' => $this->config->getNewRelicAppId()];
     $jsonArrayKeys = array_keys($json);
     foreach ($jsonArrayKeys as $jsonKey) {
         if (array_key_exists($jsonKey, $this->customParameters)) {
             unset($this->customParameters[$jsonKey]);
         }
     }
     $json = array_merge($json, $this->customParameters);
     return $this->jsonEncoder->encode($json);
 }