Moves routing into IAreaRoutes, ensures back office is redirected if installed

src/Umbraco.Web.BackOffice/Extensions/UmbracoBackOfficeApplicationBuilderExtensions.cs

@@ -1,7 +1,8 @@
 using System;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.DependencyInjection;
 using SixLabors.ImageSharp.Web.DependencyInjection;
-using Umbraco.Extensions;
+using Umbraco.Web.BackOffice.Routing;
 
 namespace Umbraco.Extensions
 {
@@ -15,18 +16,8 @@ namespace Umbraco.Extensions
 
             app.UseEndpoints(endpoints =>
             {
-                // TODO: This is temporary, 'umbraco' cannot be hard coded, needs to use GetUmbracoMvcArea()
-                // but actually we need to route all back office stuff in a back office area like we do in v8
-
-                // TODO: We will also need to detect runtime state here and redirect to the installer,
-                // Potentially switch this to dynamic routing so we can essentially disable/overwrite the back office routes to redirect to install
-                // when required, example https://www.strathweb.com/2019/08/dynamic-controller-routing-in-asp-net-core-3-0/
-
-                endpoints.MapControllerRoute("Backoffice", "/umbraco/{Action}", new
-                {
-                    Controller = "BackOffice",
-                    Action = "Default"
-                });
+                var backOfficeRoutes = app.ApplicationServices.GetRequiredService<BackOfficeAreaRoutes>();
+                backOfficeRoutes.CreateRoutes(endpoints);
             });
 
             app.UseUmbracoRuntimeMinification();