Gist of how to hook in additional OWIN authentication providers

WebApiConfig

using System.Web.Http;
using Autofac;
using Microsoft.WindowsAzure.Mobile.Service;
using Microsoft.WindowsAzure.Mobile.Service.Config;
using Owin;

namespace henrikntest09Service
{
    public static class WebApiConfig
    {
        public static void Register()
        {
            // Use this class to set configuration options for your mobile service
            ConfigOptions options = new ConfigOptions();

            // Use this class to set WebAPI configuration options
            HttpConfiguration config = ServiceConfig.Initialize(new ConfigBuilder(options, (httpConfig, autofac) =>
            {
                autofac.RegisterInstance(new AuthOwinAppBuilder(httpConfig)).As<IOwinAppBuilder>();
            }));
        }
    }

    public class AuthOwinAppBuilder : OwinAppBuilder
    {
        public AuthOwinAppBuilder(HttpConfiguration config)
            : base(config)
        {
        }

        protected override void ConfigureAuthentication(IAppBuilder appBuilder, HttpConfiguration config)
        {
            base.ConfigureAuthentication(appBuilder, config);

            // Add your own authentication modules
        }
    }
}