Imported Upstream version 4.0.0~alpha1

Former-commit-id: 806294f5ded97629b74c85c09952f2a74fe182d9

external/referencesource/System.IdentityModel/System/IdentityModel/ProductConstants.cs

@@ -0,0 +1,21 @@
+//------------------------------------------------------------
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+//------------------------------------------------------------
+
+using System;
+
+namespace System.IdentityModel
+{
+    /// <summary>
+    /// Intended for internal framework use only.
+    /// </summary>
+    internal static class ProductConstants
+    {
+#pragma warning disable 1591
+        public const string NamespaceUri = "http://schemas.microsoft.com/ws/2008/06/identity";
+        public const string ClaimValueTypeSerializationPrefix = "tn"; // for target namespace
+        public const string ClaimValueTypeSerializationPrefixWithColon = "tn:";
+        
+#pragma warning restore 1591
+    }
+}