Add HttpServerSupervisor interface

[trowski]

Closes #338. @cspray and @kelunik what do you think?

[trowski]

Should the HttpServer interface be renamed to HttpServerObserver? Maybe this is more appropriate if we are going to have two interfaces.

[kelunik]

Maybe HttpServerListener?

[trowski]

Thinking about it, either HttpServerObserver or HttpServerListener seems wrong. This is the event emitter, so HttpServerEventEmitter would be better. However that doesn't really cover getServers() either, so…

interface HttpServer extends HttpServerEventEmitter, HttpServerSupervisor {
    // public function getServers(): array; // Removed
}

interface HttpServerEventEmitter {
    public function onStart(...): void;
    public function onStop(...): void;
}

Thoughts?

[cspray]

@trowski that looks really good to me and should cover my use case quite well. I like splitting up the interfaces.

[trowski]

I removed getServers() from HttpServer, as requiring a list of SocketServer seems specific to the socket implementation and probably wouldn't apply to any implementer. I only found it used in tests where a SocketHttpServer instance was being used directly.

[trowski]

Decided to simplify and just add start and stop to HttpServer.