sendTemplate(recipientId, payload, options) {
    const message = {
      attachment: {
        type: 'template',
        payload
      }
    };
    return this.sendMessage(recipientId, message, options);
  }
Use this method if you want to send a custom template payload, like a receipt template or an airline itinerary template.
@param {Recipient|String} recipientId
@param {Object} payload The template payload.
@param {SendMessageOptions} [options]