public static AppFunc ToAppFunc(FubuRuntime runtime, OwinSettings settings = null)
{
settings = settings ?? runtime.Get<OwinSettings>();
var host = new FubuOwinHost(runtime.Routes);
AppFunc inner = host.Invoke;
AppFunc appFunc = settings.BuildAppFunc(inner, runtime.Get<IServiceFactory>());
var diagnostics = runtime.Get<DiagnosticsSettings>();
return diagnostics.WrapAppFunc(runtime, appFunc);
}