Add log for unsupported protocol with Negotiate auth (#31888)

Author: BrennanConroy

src/Security/Authentication/Negotiate/src/Internal/NegotiateLoggingExtensions.cs

@@ -18,6 +18,7 @@ internal static class NegotiateLoggingExtensions
         private static Action<ILogger, Exception?> _reauthenticating;
         private static Action<ILogger, Exception?> _deferring;
         private static Action<ILogger, string, Exception?> _negotiateError;
+        private static Action<ILogger, string, Exception?> _protocolNotSupported;
 
         static NegotiateLoggingExtensions()
         {
@@ -65,6 +66,10 @@ static NegotiateLoggingExtensions()
                 eventId: new EventId(11, "NegotiateError"),
                 logLevel: LogLevel.Debug,
                 formatString: "Negotiate error code: {error}.");
+            _protocolNotSupported = LoggerMessage.Define<string>(
+                eventId: new EventId(12, "ProtocolNotSupported"),
+                logLevel: LogLevel.Debug,
+                formatString: "Negotiate is not supported with {protocol}.");
         }
 
         public static void IncompleteNegotiateChallenge(this ILogger logger)
@@ -99,5 +104,8 @@ public static void ClientError(this ILogger logger, Exception ex)
 
         public static void NegotiateError(this ILogger logger, string error)
             => _negotiateError(logger, error, null);
+
+        public static void ProtocolNotSupported(this ILogger logger, string protocol)
+            => _protocolNotSupported(logger, protocol, null);
     }
 }

src/Security/Authentication/Negotiate/src/NegotiateHandler.cs

@@ -299,6 +299,7 @@ protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
                 // Not supported. We don't throw because Negotiate may be set as the default auth
                 // handler on a server that's running HTTP/1 and HTTP/2. We'll challenge HTTP/2 requests
                 // that require auth and they'll downgrade to HTTP/1.1.
+                Logger.ProtocolNotSupported(Request.Protocol);
                 return AuthenticateResult.NoResult();
             }