HOWTO receive event when node is selected about visnetwork HOT 1 OPEN

# In module UI function:
    visNetworkOutput(ns("network"), width = "100%", height = 800

# In module server function:
    observeEvent(input$network_highlight_color_id, {
      print(paste0("Selected items are:", input$network_highlight_color_id))
      rv_session[["highlighted_items"]] = input$network_highlight_color_id
      proxy <- visNetworkProxy(ns("network"))
      visGetPositions(proxy)
    })
    
    observeEvent(input$network_positions, {
      rv_session[["selected_positions"]] = do.call("rbind", lapply(rv_session[["highlighted_items"]], function(id) {data.frame(id=id, x=input$network_positions[[id]][["x"]], y=input$network_positions[[id]][["y"]])}))
    })