Add StateChanged(func(map[string]interface{}), more ...string) to client and server, to watch state updates with more customized detail, e.g. "completed:result" as default, e.g. pending:next\|task\|message\|result

server.go

@@ -697,3 +697,8 @@ func (srv *Server) Stop() {
 	srv.processor.stop()
 	srv.logger.Info("Processor stopped")
 }
+
+// StateChanged watch state updates, with more customized detail
+func (srv *Server) StateChanged(handler func(map[string]interface{}), more ...string) error {
+	return srv.broker.StateChanged(handler, more...)
+}