Add useragent

Author: torosent

src/Client/AzureManaged/DurableTaskSchedulerClientOptions.cs

@@ -6,7 +6,7 @@
 using Azure.Identity;
 using Grpc.Core;
 using Grpc.Net.Client;
-using Grpc.Net.Client.Configuration;
+using Microsoft.DurableTask;
 
 namespace Microsoft.DurableTask;
 
@@ -96,6 +96,9 @@ this.Credential is not null
             async (context, metadata) =>
             {
                 metadata.Add("taskhub", taskHubName);
+
+                // Add user agent header with durabletask-dotnet and DLL version from util
+                metadata.Add("user-agent", $"{DurableTaskUserAgentUtil.GetUserAgent()}");
                 if (cache == null)
                 {
                     return;

src/Shared/Core/DurableTaskVersionUtil.cs

@@ -0,0 +1,14 @@
+using System.Reflection;
+
+namespace Microsoft.DurableTask;
+
+public static class DurableTaskUserAgentUtil
+{
+    static string SdkName => "durabletask-dotnet";
+
+    public static string GetUserAgent()
+    {
+        var version = typeof(DurableTaskUserAgentUtil).Assembly.GetName().Version;
+        return $"{SdkName}/{version?.ToString() ?? "unknown"}";
+    }
+}