Overriding the default onInput handler

Hi guys,

I have a noob question about overriding the default oninput handler (see [documentation](https://github.com/FlowFuse/node-red-dashboard/blob/main/docs/contributing/guides/registration.md?plain=1#L151)).
I 'think' I do it similar as in the ui-chart node:
```
// server-side event handlers
const evts = {
onInput: function (msg, send, done) {
// My custom onInput handler
...
},
onSocket: {
...
},
beforeSend: function (msg) {
...
}
}

// inform the dashboard UI that we are adding this node
if (group) {
group.register(node, config, evts)

```
But when I inject a message into my node, this happens:
1. The message arrives in my Vue frontend code
2. The `beforeSend` of my node is called
3. My custom onInput handler above is being called

I had assumed that only 3 would happen, and not 1 and 2. Because 1 and 2 are triggered by the default onInput handler (which I have overridden)? Or perhaps I have not interpreted the documentation correctly?

Based on the msg.topic:
+ Some messages only need server side processing, so they don't need to be send to the frontend
+ Some messages need to be send to the frontend.

Can you please give me any tips about how I could achieve something like that.

Thanks!!
Bart