[Mono.Android] AndroidMessageHandler should follow HTTP-308 redirects (#8951)

Fixes: #8946

Context: 1e5bfa3

For some reason we skipped [`HttpStatusCode.PermanentRedirect`][0]
(HTTP-308) when handling redirects in 1e5bfa3.

Update `AndroidMessageHandler.HandleRedirect()` to follow an HTTP
redirect on HTTP-308 errors.

[0]: https://learn.microsoft.com/dotnet/api/system.net.httpstatuscode?view=net-8.0#system-net-httpstatuscode-permanentredirect

Author: simonrozsival

src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs

@@ -827,6 +827,7 @@ bool HandleRedirect (HttpStatusCode redirectCode, HttpURLConnection httpConnecti
 						     // what to do with the response
 
 				case HttpStatusCode.TemporaryRedirect: // 307
+				case HttpStatusCode.PermanentRedirect: // 308
 					break;
 
 				default:

tests/Mono.Android-Tests/Xamarin.Android.Net/AndroidMessageHandlerTests.cs

@@ -234,6 +234,20 @@ public async Task ServerCertificateCustomValidationCallback_Redirects ()
 			Assert.IsTrue (result.IsSuccessStatusCode);
 		}
 
+		[Test]
+		public async Task AndroidMessageHandlerFollows308PermanentRedirect ()
+		{
+			int callbackCounter = 0;
+
+			var handler = new AndroidMessageHandler ();
+
+			var client = new HttpClient (handler);
+			var result = await client.GetAsync ("https://httpbin.org/redirect-to?url=https://www.microsoft.com/&status_code=308");
+
+			Assert.IsTrue (result.IsSuccessStatusCode);
+			Assert.AreEqual ("https://www.microsoft.com/", result.RequestMessage.RequestUri.ToString ());
+		}
+
 		private async Task AssertRejectsRemoteCertificate (Func<Task> makeRequest)
 		{
 			// there is a difference between the exception that's thrown in the .NET build and the legacy Xamarin