Gets virtual page routing working, now just need to document.

src/Umbraco.Web.Common/ApplicationModels/VirtualPageApplicationModelProvider.cs

@@ -0,0 +1,61 @@
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.AspNetCore.Mvc.ApplicationModels;
+using Umbraco.Core;
+using Umbraco.Core.Models.PublishedContent;
+using Umbraco.Web.Common.Controllers;
+
+namespace Umbraco.Web.Common.ApplicationModels
+{
+    /// <summary>
+    /// Applies the <see cref="VirtualPageConvention"/> to any action on a controller that is <see cref="IVirtualPageController"/>
+    /// </summary>
+    public class VirtualPageApplicationModelProvider : IApplicationModelProvider
+    {
+        private readonly List<IActionModelConvention> _actionModelConventions = new List<IActionModelConvention>()
+        {
+            new VirtualPageConvention()
+        };
+
+        /// <inheritdoc />
+        /// <summary>
+        /// Will execute after <see cref="DefaultApplicationModelProvider"/>
+        /// </summary>
+        public int Order => 0;
+
+        /// <inheritdoc />
+        public void OnProvidersExecuted(ApplicationModelProviderContext context) { }
+
+        /// <inheritdoc />
+        public void OnProvidersExecuting(ApplicationModelProviderContext context)
+        {
+            foreach (ControllerModel controller in context.Result.Controllers)
+            {
+                if (!IsVirtualPageController(controller))
+                {
+                    continue;
+                }
+
+                foreach (ActionModel action in controller.Actions.ToList())
+                {
+                    if (action.ActionName == nameof(IVirtualPageController.FindContent)
+                        && action.ActionMethod.ReturnType == typeof(IPublishedContent))
+                    {
+                        // this is not an action, it's just the implementation of IVirtualPageController
+                        controller.Actions.Remove(action);
+                    }
+                    else
+                    {
+                        foreach (IActionModelConvention convention in _actionModelConventions)
+                        {
+                            convention.Apply(action);
+                        }
+                    }
+                }
+            }
+        }
+
+        private bool IsVirtualPageController(ControllerModel controller)
+            => controller.ControllerType.Implements<IVirtualPageController>();
+    }
+}