feat: added custom signal for pre sales order created

business/signals.py

@@ -0,0 +1,21 @@
+"""business domain signals.
+
+We use domain-level signals (instead of model post_save) to:
+- keep semantics clean (only fire on business "create" flow)
+- allow passing explicit actor (created_by / operator)
+- keep integrations in handlers
+
+NOTE:
+Signals should be triggered via transaction.on_commit to avoid firing when a
+transaction rolls back.
+"""
+
+from django.dispatch import Signal
+
+# Fired when a PreSalesOrder (and its items) is created via service layer.
+# Payload:
+# - instance: PreSalesOrder
+# - created_by: Django User (may be None)
+# - operator: Employee (may be None)
+# - items_count: int
+pre_sales_order_created = Signal()