Feat: set start metadata in pipeline

This is needed so that we can send correlation id for workflow runs in Dograh MPS

api/services/pipecat/pipeline_builder.py

@@ -105,6 +105,7 @@ def create_pipeline_task(pipeline, workflow_run_id, audio_config: AudioConfig =
         enable_usage_metrics=True,
         send_initial_empty_metrics=False,
         enable_heartbeats=True,
+        start_metadata={"workflow_run_id": workflow_run_id},
     )
 
     # If audio_config is provided, set the audio sample rates