Implement BearerTokenChallengeAuthenticationPolicy

sdk/core/Azure.Core/src/Azure.Core.csproj

@@ -26,6 +26,7 @@
   <ItemGroup>
     <Compile Remove="Shared\**\*.cs" />
     <Compile Include="Shared\Argument.cs" />
+    <Compile Include="Shared\AzureCoreSharedEventSource.cs" />
     <Compile Include="Shared\AzureKeyCredentialPolicy.cs" />
     <Compile Include="Shared\AzureSasCredentialSynchronousPolicy.cs" />
     <Compile Include="Shared\Base64Url.cs" />

sdk/core/Azure.Core/src/Shared/AzureCoreSharedEventSource.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Diagnostics.Tracing;
+
+namespace Azure.Core.Diagnostics
+{
+    [EventSource(Name = EventSourceName)]
+    internal sealed class AzureCoreSharedEventSource : EventSource
+    {
+        private const string EventSourceName = "Azure-Core-Shared";
+
+        private const int BackgroundRefreshFailedEvent = 19;
+
+        private AzureCoreSharedEventSource() : base(EventSourceName, EventSourceSettings.Default, AzureEventSourceListener.TraitName, AzureEventSourceListener.TraitValue) { }
+
+        public static AzureCoreSharedEventSource Singleton { get; } = new AzureCoreSharedEventSource();
+
+        [Event(BackgroundRefreshFailedEvent, Level = EventLevel.Informational, Message = "Background token refresh [{0}] failed with exception {1}")]
+        public void BackgroundRefreshFailed(string requestId, string exception)
+        {
+            WriteEvent(BackgroundRefreshFailedEvent, requestId, exception);
+        }
+    }
+}