Use W3C format in frontend-backend

samples/frontend-backend/backend/Program.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Hosting;
 
@@ -11,6 +12,7 @@ namespace Backend
     {
         public static void Main(string[] args)
         {
+            Activity.DefaultIdFormat = ActivityIdFormat.W3C;
             CreateHostBuilder(args).Build().Run();
         }
 

samples/frontend-backend/frontend/Program.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Diagnostics;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.Hosting;
 
@@ -11,6 +12,7 @@ namespace Frontend
     {
         public static void Main(string[] args)
         {
+            Activity.DefaultIdFormat = ActivityIdFormat.W3C;
             CreateHostBuilder(args).Build().Run();
         }