docs: public static MessageSendResult messageMassPreview(String access_token, Preview preview) {
          String previewJson = JsonUtil.toJSONString(preview);
          HttpUriRequest httpUriRequest = RequestBuilder.post()
                  .setHeader(jsonHeader)
                  .setUri(BASE_URI + "/cgi-bin/message/mass/preview")
                  .addParameter(PARAM_ACCESS_TOKEN, API.accessToken(access_token))
                  .setEntity(new StringEntity(previewJson, Charset.forName("utf-8")))
                  .build();
          return LocalHttpClient.executeJsonResult(httpUriRequest, MessageSendResult.class);
      }