docs: public Elasticsearch failureHandlerCustom(Class<? extends ActionRequestFailureHandler> failureHandlerClass) {
  		internalProperties.putString(CONNECTOR_FAILURE_HANDLER, ElasticsearchValidator.CONNECTOR_FAILURE_HANDLER_VALUE_CUSTOM);
  		internalProperties.putClass(CONNECTOR_FAILURE_HANDLER_CLASS, failureHandlerClass);
  		return this;
  	}