Add parent trace context information when scheduling an orchestration (#358)

Author: bachuv

src/Client/Grpc/GrpcDurableTaskClient.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Diagnostics;
 using System.Text;
 using Google.Protobuf.WellKnownTypes;
 using Microsoft.DurableTask.Client.Entities;
@@ -85,6 +86,24 @@ public override async Task<string> ScheduleNewOrchestrationInstanceAsync(
             Input = this.DataConverter.Serialize(input),
         };
 
+        if (Activity.Current?.Id != null || Activity.Current?.TraceStateString != null)
+        {
+            if (request.ParentTraceContext == null)
+            {
+                request.ParentTraceContext = new P.TraceContext();
+            }
+
+            if (Activity.Current?.Id != null)
+            {
+                request.ParentTraceContext.TraceParent = Activity.Current?.Id;
+            }
+
+            if (Activity.Current?.TraceStateString != null)
+            {
+                request.ParentTraceContext.TraceState = Activity.Current?.TraceStateString;
+            }
+        }
+
         DateTimeOffset? startAt = options?.StartAt;
         this.logger.SchedulingOrchestration(
             request.InstanceId,