How to use the mobx-keystone.onActionMiddleware function in mobx-keystone

// in clients we use the sync new model ids version to make sure that
      // any model ids that were generated in the server side end up being
      // the same in the client side
      applySerializedActionAndSyncNewModelIds(rootStore, actionCall)
    } finally {
      serverAction = wasServerAction
    }
  }

  // listen to action messages to be replicated into the local root store
  server.onMessage(actionCall => {
    runServerActionLocally(actionCall)
  })

  // also listen to local actions, cancel them and send them to the server
  onActionMiddleware(rootStore, {
    onStart(actionCall, ctx) {
      if (!serverAction) {
        // if the action does not come from the server cancel it silently
        // and send it to the server
        // it will then be replicated by the server and properly executed
        server.sendMessage(serializeActionCall(actionCall, rootStore))

        ctx.data[cancelledActionSymbol] = true // just for logging purposes

        // "cancel" the action by returning undefined
        return {
          result: ActionTrackingResult.Return,
          value: undefined,
        }
      } else {
        // just run the server action unmodified