docs: public OpenPgpMetadata addOxMessage(Message message, Set<OpenPgpContact> contacts, List<ExtensionElement> payload)
              throws SmackException.NotLoggedInException, IOException, PGPException {
  
          HashSet<OpenPgpContact> recipients = new HashSet<>(contacts);
          OpenPgpContact self = openPgpManager.getOpenPgpSelf();
          recipients.add(self);
  
          OpenPgpElementAndMetadata openPgpElementAndMetadata = signAndEncrypt(recipients, payload);
          message.addExtension(openPgpElementAndMetadata.getElement());
  
          // Set hints on message
          ExplicitMessageEncryptionElement.set(message,
                  ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.openpgpV0);
          StoreHint.set(message);
          setOXBodyHint(message);
  
          return openPgpElementAndMetadata.getMetadata();
      }