code: public static Response post(URI uri, String body, ContentType contentType)
          throws URISyntaxException, HttpException {
          return postBody(new HttpPost(uri), body, contentType, null, null);
      }
docs: Performs an HTTP POST on the given URL.
  
  @param uri         The URI to connect to.
  @param body        The POST body.
  @param contentType The ContentType of the POST body.
  @return The HTTP response as Response object.
  @throws URISyntaxException
  @throws HttpException