fix - device pre register & exception handling with json response

apps/product/services/quota_distribution_service.py

@@ -0,0 +1,28 @@
+from django.db.models import Sum
+
+from apps.product import models as product_models
+
+
+class QuotaDistributionService:
+    """
+    Service layer to manage multiple quota distributions as one unified entity.
+    Used for organization-based views and POS operations.
+    """
+
+    def __init__(self, quota, organization):
+        self.quota = quota
+        self.organization = organization
+        self.distribution = product_models.QuotaDistribution.objects.filter(
+            quota=quota,
+            assigned_organization=organization,
+            quota__is_closed=False,
+            warehouse_entry__gt=0
+        ).first()
+
+        @property
+        def total_weight(self):
+            return self.distribution.aggregate(
+                total=Sum('weight')
+            )['total'] or 0
+
+        pass