code: @NonNull
      public ListenerToken addDocumentReplicationListener(@NonNull DocumentReplicationListener listener) {
          if (listener == null) { throw new IllegalArgumentException("listener cannot be null."); }
  
          return addDocumentReplicationListener(null, listener);
      }
docs: Set the given DocumentReplicationListener to the this replicator.
  
  @param listener
  @return ListenerToken A token to remove the handler later