feat: added wecom notify when printing_job production was completed(new status) and shipment was created

printing/signals.py

@@ -15,3 +15,9 @@ from django.dispatch import Signal
 # - created_by: Django User (may be None)
 printing_order_created = Signal()
 
+# Fired when a PrintingJob is explicitly marked as production completed
+# via business service.
+# Payload:
+# - instance: PrintingJob
+# - triggered_by: Django User (may be None)
+printing_job_production_completed = Signal()