Log heartbeat pulse generation in debug level

Add a debug-level log message to indicate when the heartbeat pulse is generated. This improves traceability and helps in diagnosing runtime behavior during development and debugging.

src/modules/Elsa.Workflows.Runtime/Middleware/Workflows/HeartbeatMiddleware.cs

@@ -45,6 +45,7 @@ public class WorkflowHeartbeatMiddleware(WorkflowMiddlewareDelegate next, IOptio
         {
             try
             {
+                _logger.LogDebug("Generating pulse");
                 await _pulseAction();
                 _timer.Change(_interval, Timeout.InfiniteTimeSpan);
             }