ConnectionStateListener gets overwritten by library

[keryigit]

Describe the bug
The AgvController._subscribeOnStarted method is asynchonrously overwriting user registered connection state listeners.

Is this a regression?
No

To Reproduce
Minimal steps to reproduce the behavior:

1. Override the method AgvController.onStarted like this:

       class MyAgvController extends AgvController {
       ...
        protected async onStarted() {
           await super.onStarted()
           this.registerConnectionStateChange((st, ps) => { console.log(`connection state change ${ps} -> ${st}`) })
        }
        ...
        }

2. Run MyAgvController.start()
3. Wait for connection
4. Disconnect externally (eg. disable wifi / unplug ethernet cable)
5. Wait > 15s
6. Reconnect externally

Expected behavior
The disconnect state change (online -> offline) should be called through our registered callback.

Environment:

• Package Version: [1.4.0]
• Node.js Version: [20.11.1]
• OS: [Ubuntu 20.04]

Additional context
The problem lies in the asynchronous callback in the AgvController.attach method:

    private _attachAdapter() {
        this.debug("Invoking attach handler");
        this._agvAdapter.attach({
            attached: async initialState => { // this is an async callback
                // Ensure subscriptions on orders and instant actions are
                // registered with the broker before publishing the initial
                // state. A Master Control may observe this state to immediately
                // trigger initial instant actions or orders.
                this.updatePartialState(initialState, false);
                await this._subscribeOnStarted();
                this._publishCurrentState();
            },
        });
    }
    ...
    private async _subscribeOnStarted() {
        // First, subscribe to orders and instant actions.
        await this.subscribe(Topic.Order, order => this._processOrder(order));
        await this.subscribe(Topic.InstantActions, actions => this._processInstantActions(actions));

        // Ensure State is reported immediately once after client is online again.
        console.log(`_subscribeOnStarted register connection listener@ ${Date.now()}`);
        this.registerConnectionStateChange((currentState, prevState) => { // this is called after all subscriptions are done, which may happen AFTER onStarted has returned, and after we registered our listener
            if (currentState === "online" && prevState !== "online") {
                this._publishCurrentState();
            }
        });

        this._setupPublishVisualizationInterval();
    }

I suggest you use a second private class property to store the callback used in _subscribeOnStarted instead of the public callback.