Obsolete AuthenticationManager (#866)

Author: HaoK

src/Microsoft.AspNetCore.Http.Abstractions/Authentication/AuthenticationManager.cs

@@ -9,6 +9,7 @@
 
 namespace Microsoft.AspNetCore.Http.Authentication
 {
+    [Obsolete("This is obsolete and will be removed in a future version. See https://go.microsoft.com/fwlink/?linkid=845470.")]
     public abstract class AuthenticationManager
     {
         /// <summary>

src/Microsoft.AspNetCore.Http/Authentication/DefaultAuthenticationManager.cs

@@ -11,6 +11,7 @@
 
 namespace Microsoft.AspNetCore.Http.Authentication.Internal
 {
+    [Obsolete("This is obsolete and will be removed in a future version. See https://go.microsoft.com/fwlink/?linkid=845470.")]
     public class DefaultAuthenticationManager : AuthenticationManager
     {
         // Lambda hoisted to static readonly field to improve inlining https://github.com/dotnet/roslyn/issues/13624

src/Microsoft.AspNetCore.Http/DefaultHttpContext.cs

@@ -28,7 +28,11 @@ public class DefaultHttpContext : HttpContext
 
         private HttpRequest _request;
         private HttpResponse _response;
+
+#pragma warning disable CS0618 // Type or member is obsolete
         private AuthenticationManager _authenticationManager;
+#pragma warning restore CS0618 // Type or member is obsolete
+
         private ConnectionInfo _connection;
         private WebSocketManager _websockets;
 
@@ -66,7 +70,9 @@ public virtual void Uninitialize()
             }
             if (_authenticationManager != null)
             {
+#pragma warning disable CS0618 // Type or member is obsolete
                 UninitializeAuthenticationManager(_authenticationManager);
+#pragma warning restore CS0618 // Type or member is obsolete
                 _authenticationManager = null;
             }
             if (_connection != null)
@@ -196,7 +202,9 @@ protected virtual void UninitializeHttpResponse(HttpResponse instance) { }
         protected virtual ConnectionInfo InitializeConnectionInfo() => new DefaultConnectionInfo(Features);
         protected virtual void UninitializeConnectionInfo(ConnectionInfo instance) { }
 
+        [Obsolete("This is obsolete and will be removed in a future version. See https://go.microsoft.com/fwlink/?linkid=845470.")]
         protected virtual AuthenticationManager InitializeAuthenticationManager() => new DefaultAuthenticationManager(this);
+        [Obsolete("This is obsolete and will be removed in a future version. See https://go.microsoft.com/fwlink/?linkid=845470.")]
         protected virtual void UninitializeAuthenticationManager(AuthenticationManager instance) { }
 
         protected virtual WebSocketManager InitializeWebSocketManager() => new DefaultWebSocketManager(Features);