migrate site id to varchar instead of int

backend/apps/farms/serializers.py

@@ -4,7 +4,9 @@ from apps.accounts.serializers import PkAsIdMixin
 from apps.farms.models import Cycle, Flock, Kandang, Site
 
 
-class SiteSerializer(PkAsIdMixin, serializers.ModelSerializer):
+class SiteSerializer(serializers.ModelSerializer):
+    # Slug PK (matches farm site_id); do not use IntegerField PkAsIdMixin.
+    id = serializers.CharField(source="pk", read_only=True)
     owner_name = serializers.CharField(source="user.display_name", read_only=True)
 
     class Meta: