feat(payment): add is_expired filter and serializer method for payment expiration tracking ✨

billing/serializers.py

@@ -5,6 +5,10 @@ from devices.serializers import DeviceSerializer
 
 class PaymentSerializer(serializers.ModelSerializer):
     devices = DeviceSerializer(many=True, read_only=True)
+    is_expired = serializers.SerializerMethodField()
+
+    def get_is_expired(self, obj):
+        return obj.is_expired
 
     class Meta:  # type: ignore
         model = Payment