WCF support for ASP.Net Core

Provides middleware for ASP.Net Core for wiring up a WCF ServiceHost instance and directing requests to it. This is a bit more complicated than just establishing a binding and dispatcher.

public void ConfigureServices(IServiceCollection services)
{
    services.AddServiceModel();
}
        
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseServiceHost<MathService>("/math", configure =>
    {
        configure.AddServiceEndpoint<IMathService>("");
        configure.AddServiceEndpoint<IMathService>("/2");
    });
}

I've done a few things internally that are sort of weird.

A custom baseUri is established with a custom scheme: aspnetcore. Service endpoints register and listen against these addresses: aspnetcore:/GUID/path. Paths are rewritten into these internal paths as they enter the middleware, and dispatched to a router. The router routes to a set of queues. The queues exist because ChannelListeners start up and register queues to listen to.

This lets us use the existing ServiceHost class. And thus eventually piggyback on existing ServiceHost extensions: like Autofac integration. And it keeps the dispatch/contract discovery stuff in WCF. The only unfortunate part about this is ServiceHost is kind of heavy. Seems to spawn a lot of channel listeners, and invoke OnBeginAccept a lot. So, we're using semaphores to lease those out.

Also, I'm using completely custom bindings. BasicHttpBinding is not used, of course. AspNetCoreBasicBinding is instead doing the same setup. I want a AspnetCoreWSBinding!