code: public WebhookResponse send(String url, Payload payload) throws IOException {
          SlackHttpClient httpClient = getHttpClient();
          Response httpResponse = httpClient.postJsonPostRequest(url, payload);
          String body = httpResponse.body().string();
          httpClient.runHttpResponseListeners(httpResponse, body);
  
          return WebhookResponse.builder()
                  .code(httpResponse.code())
                  .message(httpResponse.message())
                  .body(body)
                  .build();
      }
docs: Send a data to Incoming Webhook endpoint.