Add project files.

src/clients/Elsa.Api.Client/RealTime/Messages/ActivityExecutingMessage.cs

@@ -0,0 +1,10 @@
+using Elsa.Api.Client.Resources.ActivityExecutions.Models;
+
+namespace Elsa.Api.Client.RealTime.Messages;
+
+/// <summary>
+/// Contains information about the activity executing event.
+/// </summary>
+/// <param name="ActivityId">The ID of the activity.</param>
+/// <param name="Stats">Execution stats about the activity.</param>
+public record ActivityExecutingMessage(string ActivityId, ActivityExecutionStats Stats);