Lazy load ITwoFactorChallengeHandler in LoginManager.

So that `GitHub.App` is only loaded when actually needed.

Author: grokys

src/GitHub.Api/LoginManager.cs

@@ -14,7 +14,7 @@ public class LoginManager : ILoginManager
     {
         readonly string[] scopes = { "user", "repo", "gist", "write:public_key" };
         readonly IKeychain keychain;
-        readonly ITwoFactorChallengeHandler twoFactorChallengeHandler;
+        readonly Lazy<ITwoFactorChallengeHandler> twoFactorChallengeHandler;
         readonly string clientId;
         readonly string clientSecret;
         readonly string authorizationNote;
@@ -31,7 +31,7 @@ public class LoginManager : ILoginManager
         /// <param name="fingerprint">The machine fingerprint.</param>
         public LoginManager(
             IKeychain keychain,
-            ITwoFactorChallengeHandler twoFactorChallengeHandler,
+            Lazy<ITwoFactorChallengeHandler> twoFactorChallengeHandler,
             string clientId,
             string clientSecret,
             string authorizationNote = null,
@@ -194,7 +194,7 @@ async Task<ApplicationAuthorization> HandleTwoFactorAuthorization(
         {
             for (;;)
             {
-                var challengeResult = await twoFactorChallengeHandler.HandleTwoFactorException(exception);
+                var challengeResult = await twoFactorChallengeHandler.Value.HandleTwoFactorException(exception);
 
                 if (challengeResult == null)
                 {
@@ -218,7 +218,7 @@ async Task<ApplicationAuthorization> HandleTwoFactorAuthorization(
                     }
                     catch (Exception e)
                     {
-                        await twoFactorChallengeHandler.ChallengeFailed(e);
+                        await twoFactorChallengeHandler.Value.ChallengeFailed(e);
                         await keychain.Delete(hostAddress).ConfigureAwait(false);
                         throw;
                     }

src/GitHub.VisualStudio/GitHubPackage.cs

@@ -1,6 +1,7 @@
 using System;
 using System.ComponentModel.Composition;
 using System.Diagnostics;
+using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -211,11 +212,10 @@ async Task<object> CreateService(IAsyncServiceContainer container, CancellationT
             {
                 var serviceProvider = await GetServiceAsync(typeof(IGitHubServiceProvider)) as IGitHubServiceProvider;
                 var keychain = serviceProvider.GetService<IKeychain>();
-                var twoFaHandler = serviceProvider.GetService<ITwoFactorChallengeHandler>();
 
                 return new LoginManager(
                     keychain,
-                    twoFaHandler,
+                    new Lazy<ITwoFactorChallengeHandler>(() => serviceProvider.GetService<ITwoFactorChallengeHandler>()),
                     ApiClientConfiguration.ClientId,
                     ApiClientConfiguration.ClientSecret,
                     ApiClientConfiguration.AuthorizationNote,