docs: public OutgoingFileTransfer createOutgoingFileTransfer(EntityFullJid userID) {
          // We need to create outgoing file transfers with a full JID since this method will later
          // use XEP-0095 to negotiate the stream. This is done with IQ stanzas that need to be addressed to a full JID
          // in order to reach an client entity.
          if (userID == null) {
              throw new IllegalArgumentException("userID was null");
          }
  
          return new OutgoingFileTransfer(connection().getUser(), userID,
                  FileTransferNegotiator.getNextStreamID(),
                  fileTransferNegotiator);
      }