Wires up DI for cross wiring correctly ensuring that it occurs at the very end of ConfigureServices, updates tests accordingly, fixes a few other things.

src/Umbraco.Web.UI.NetCore/Program.cs

@@ -1,11 +1,7 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Hosting;
-using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Hosting;
-using Microsoft.Extensions.Logging;
+using Serilog;
+using Umbraco.Core.Composing;
 
 namespace Umbraco.Web.UI.BackOffice
 {
@@ -19,7 +15,9 @@ namespace Umbraco.Web.UI.BackOffice
         }
 
         public static IHostBuilder CreateHostBuilder(string[] args) =>
-            Host.CreateDefaultBuilder(args)
-                .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); });
+            Host.CreateDefaultBuilder(args)                
+                .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); })
+                .UseUmbraco()
+                .UseSerilog();
     }
 }

src/Umbraco.Web.UI.NetCore/Startup.cs

@@ -19,8 +19,8 @@ namespace Umbraco.Web.UI.BackOffice
         // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
         public void ConfigureServices(IServiceCollection services)
         {
+            services.AddUmbracoCore();
             services.AddUmbracoWebsite();
-            services.AddUmbracoBackOffice();
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.