feat: Add old_balance flag to vacation creation

- Add `is_old_balance` to vacation serializer
- Pass `is_old_balance` to Vacation model creation
- Pass `is_old_balance` to VacationNotification

Author: Mahmoud-Emad

server/cshr/views/vacations.py

@@ -441,6 +441,7 @@ def post(self, request: Request, user_id: str) -> Response:
             reason = serializer.validated_data.get("reason")
             from_date = serializer.validated_data.get("from_date")
             end_date = serializer.validated_data.get("end_date")
+            is_old_balance = request.data.get("old_balance", False)
             applying_user = get_user_by_id(user_id)
 
             if applying_user is None:
@@ -456,6 +457,7 @@ def post(self, request: Request, user_id: str) -> Response:
                 reason=reason,
                 from_date=from_date,
                 end_date=end_date,
+                is_old_balance=is_old_balance,
             )
 
             vacation_days = 0
@@ -480,6 +482,7 @@ def post(self, request: Request, user_id: str) -> Response:
                 type=TYPE_CHOICES.VACATIONS,
                 status=STATUS_CHOICES.APPROVED,
                 actual_days=vacation_days,
+                is_old_balance=is_old_balance,
             )
 
             notification_service = VacationNotification(