Adding 2FA Authenticator Support (#66)

* Adding support for 2fa, more auth options

* WIP getting auth stuff working

* Added Manage views. 2FA working now for MVC app.

* Switching to using a controller for no-UI logout scenario

* Adding Razor Pages impl of 2FA auth stuff. Works.

src/WebRazorPages/Extensions/UrlHelperExtensions.cs

@@ -0,0 +1,33 @@
+namespace Microsoft.AspNetCore.Mvc
+{
+    public static class UrlHelperExtensions
+    {
+        public static string GetLocalUrl(this IUrlHelper urlHelper, string localUrl)
+        {
+            if (!urlHelper.IsLocalUrl(localUrl))
+            {
+                return urlHelper.Page("/Index");
+            }
+
+            return localUrl;
+        }
+
+        public static string EmailConfirmationLink(this IUrlHelper urlHelper, string userId, string code, string scheme)
+        {
+            return urlHelper.Page(
+                "/Account/ConfirmEmail",
+                pageHandler: null,
+                values: new { userId, code },
+                protocol: scheme);
+        }
+
+        public static string ResetPasswordCallbackLink(this IUrlHelper urlHelper, string userId, string code, string scheme)
+        {
+            return urlHelper.Page(
+                "/Account/ResetPassword",
+                pageHandler: null,
+                values: new { userId, code },
+                protocol: scheme);
+        }
+    }
+}