Update google token endpoint to v4

Author: HaoK

src/Microsoft.AspNetCore.Authentication.Google/GoogleDefaults.cs

@@ -9,7 +9,7 @@ public static class GoogleDefaults
 
         public static readonly string AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/auth";
 
-        public static readonly string TokenEndpoint = "https://www.googleapis.com/oauth2/v3/token";
+        public static readonly string TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token";
 
         public static readonly string UserInformationEndpoint = "https://www.googleapis.com/plus/v1/people/me";
     }

test/Microsoft.AspNetCore.Authentication.Test/Google/GoogleMiddlewareTests.cs

@@ -299,7 +299,7 @@ public async Task ReplyPathWillAuthenticateValidAuthorizeCodeAndState(string cla
                 {
                     Sender = req =>
                     {
-                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v3/token")
+                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v4/token")
                         {
                             return ReturnJsonResponse(new
                             {
@@ -489,7 +489,7 @@ public async Task AuthenticatedEventCanGetRefreshToken()
                 {
                     Sender = req =>
                     {
-                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v3/token")
+                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v4/token")
                         {
                             return ReturnJsonResponse(new
                             {
@@ -569,7 +569,7 @@ public async Task NullRedirectUriWillRedirectToSlash()
                 {
                     Sender = req =>
                     {
-                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v3/token")
+                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v4/token")
                         {
                             return ReturnJsonResponse(new
                             {
@@ -659,7 +659,7 @@ public async Task ValidateAuthenticatedContext()
                 {
                     Sender = req =>
                     {
-                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v3/token")
+                        if (req.RequestUri.AbsoluteUri == "https://www.googleapis.com/oauth2/v4/token")
                         {
                             return ReturnJsonResponse(new
                             {