Support custom EventListener in DatadogEventListener.Factory about dd-sdk-android

[xgouchet]

Hi @neworld , and thanks a lot for the feature request.

Indeed this is not something we considered, but is definitely something we need to do. We added that to our roadmap and we'll try to deliver it in a timely manner.

If you want to, you can submit a Pull Request (if you do, make sure to read our Contributing guidelines).

[xgouchet]

As you said in the PR, it's indeed safer to do it the other way 'round and let your Listener call ours.

You can do this easily like so:

class CustomEventListener(
    private val delegate: EventListener
) : EventListener() {

    override fun connectStart(call: Call, inetSocketAddress: InetSocketAddress, proxy: Proxy) {
        super.connectStart(call, inetSocketAddress, proxy)
        delegate.connectStart(call, inetSocketAddress, proxy)
    }
    
    // …

    class Factory : EventListener.Factory {
        private val datadogFactory = DatadogEventListener.Factory()

        override fun create(call: Call): EventListener {
            val delegate = datadogFactory.create(call)

            return CustomEventListener(delegate)
        }
    }
}