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/Pages/Account/Manage/GenerateRecoveryCodes.cshtml.cs

@@ -0,0 +1,48 @@
+using Infrastructure.Identity;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.Extensions.Logging;
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Microsoft.eShopWeb.RazorPages.Pages.Account.Manage
+{
+    public class GenerateRecoveryCodesModel : PageModel
+    {
+        private readonly UserManager<ApplicationUser> _userManager;
+        private readonly ILogger<GenerateRecoveryCodesModel> _logger;
+
+        public GenerateRecoveryCodesModel(
+            UserManager<ApplicationUser> userManager,
+            ILogger<GenerateRecoveryCodesModel> logger)
+        {
+            _userManager = userManager;
+            _logger = logger;
+        }
+
+        public string[] RecoveryCodes { get; set; }
+
+        public async Task<IActionResult> OnGetAsync()
+        {
+            var user = await _userManager.GetUserAsync(User);
+            if (user == null)
+            {
+                throw new ApplicationException($"Unable to load user with ID '{_userManager.GetUserId(User)}'.");
+            }
+
+            if (!user.TwoFactorEnabled)
+            {
+                throw new ApplicationException($"Cannot generate recovery codes for user with ID '{user.Id}' as they do not have 2FA enabled.");
+            }
+
+            var recoveryCodes = await _userManager.GenerateNewTwoFactorRecoveryCodesAsync(user, 10);
+            RecoveryCodes = recoveryCodes.ToArray();
+
+            _logger.LogInformation("User with ID '{UserId}' has generated new 2FA recovery codes.", user.Id);
+
+            return Page();
+        }
+    }
+}