code: public InputStream post(URI uri, String json) {
          HttpConnection connection = Http.POST(uri,
                  "application/json");
          if (json != null && !json.isEmpty()) {
              connection.setRequestBody(json);
          }
          return executeToInputStream(connection);
      }
docs: <p>Performs a HTTP POST request with JSON request body.</p>
  <p>The stream <b>must</b> be closed after use.</p>
  
  @return Input stream with response