Maintenance page when in upgrade state (#13551)

* Added functionality to show maintenance page and fixed issues with showing custom api controllers and 404 page, when umbraco had been in install or upgrade state

* Fixed Tests

* Fixed typo

* Fixed issue with login screen redirecting to website when in upgrade state, instead of backoffice

src/Umbraco.Web.Website/Routing/FrontEndRoutes.cs

@@ -41,13 +41,22 @@ public sealed class FrontEndRoutes : IAreaRoutes
     /// <inheritdoc />
     public void CreateRoutes(IEndpointRouteBuilder endpoints)
     {
-        if (_runtimeState.Level != RuntimeLevel.Run)
+        switch (_runtimeState.Level)
         {
-            return;
+            case RuntimeLevel.Install:
+            case RuntimeLevel.Upgrade:
+            case RuntimeLevel.Run:
+
+                AutoRouteSurfaceControllers(endpoints);
+                AutoRouteFrontEndApiControllers(endpoints);
+                break;
+            case RuntimeLevel.BootFailed:
+            case RuntimeLevel.Unknown:
+            case RuntimeLevel.Boot:
+                break;
         }
 
-        AutoRouteSurfaceControllers(endpoints);
-        AutoRouteFrontEndApiControllers(endpoints);
+
     }
 
     /// <summary>

src/Umbraco.Web.Website/Routing/UmbracoRouteValueTransformer.cs

@@ -117,9 +117,20 @@ public class UmbracoRouteValueTransformer : DynamicRouteValueTransformer
     public override async ValueTask<RouteValueDictionary> TransformAsync(
         HttpContext httpContext, RouteValueDictionary values)
     {
-        // If we aren't running, then we have nothing to route
-        if (_runtime.Level != RuntimeLevel.Run)
+        // If we aren't running, then we have nothing to route. We allow the frontend to continue while in upgrade mode.
+        if (_runtime.Level != RuntimeLevel.Run && _runtime.Level != RuntimeLevel.Upgrade)
         {
+            if (_runtime.Level == RuntimeLevel.Install)
+            {
+                return new RouteValueDictionary()
+                {
+                    //TODO figure out constants
+                    [ControllerToken] = "Install",
+                    [ActionToken] = "Index",
+                    [AreaToken] = Constants.Web.Mvc.InstallArea,
+                };
+            }
+
             return null!;
         }
 
@@ -184,6 +195,7 @@ public class UmbracoRouteValueTransformer : DynamicRouteValueTransformer
             // our default 404 page but we cannot return route values now because
             // it's possible that a developer is handling dynamic routes too.
             // Our 404 page will be handled with the NotFoundSelectorPolicy
+
             return null!;
         }