Update settings.h

Author: zarinatlupova

src/client/impl/ydb_internal/rpc_request_settings/settings.h

@@ -24,6 +24,12 @@ struct TRpcRequestSettings {
         rpcSettings.TraceId = settings.TraceId_;
         rpcSettings.RequestType = settings.RequestType_;
         rpcSettings.Header = settings.Header_;
+
+        // Add TraceParent to headers (if it is set)
+        if (!settings.TraceParent_.empty()) {
+            rpcSettings.Header.emplace_back("traceparent", settings.TraceParent_);
+        }
+        
         rpcSettings.PreferredEndpoint = preferredEndpoint;
         rpcSettings.EndpointPolicy = endpointPolicy;
         rpcSettings.UseAuth = true;