code: public static Message receiptMessageFor(Message messageWithReceiptRequest) {
          String stanzaId = messageWithReceiptRequest.getStanzaId();
          if (StringUtils.isNullOrEmpty(stanzaId)) {
              return null;
          }
          Message message = new Message(messageWithReceiptRequest.getFrom(), messageWithReceiptRequest.getType());
          message.addExtension(new DeliveryReceipt(stanzaId));
          return message;
      }
docs: Create and return a new message including a delivery receipt extension for the given message.
  <p>
  If {@code messageWithReceiptRequest} does not have a Stanza ID set, then {@code null} will be returned.
  </p>
  
  @param messageWithReceiptRequest the given message with a receipt request extension.
  @return a new message with a receipt or <code>null</code>.
  @since 4.1