docs: public static void addBody(Message message, XHTMLText xhtmlText) {
          XHTMLExtension xhtmlExtension = XHTMLExtension.from(message);
          if (xhtmlExtension == null) {
              // Create an XHTMLExtension and add it to the message
              xhtmlExtension = new XHTMLExtension();
              message.addExtension(xhtmlExtension);
          }
          // Add the required bodies to the message
          xhtmlExtension.addBody(xhtmlText.toXML());
      }