UseBuilder should take optional Action<IServiceCollection>

[davidfowl]

To make it easier to configure services in the ASP.NET 5 pipeline when exposed via Owin

[muratg]

Won't the overload with Action<IApplicationBuilder> be enough for that? It has a ServiceProvider property.

[Tratcher]

Except ServiceProvider is null:

HttpAbstractions/src/Microsoft.AspNet.Owin/OwinExtensions.cs

Line 72 in f475e53

var builder = new ApplicationBuilder(serviceProvider: null);