fix(shop): prevent division by zero in product rating calculation

The get_rating method in ProductSerializer did not handle cases where a product
had no reviews, resulting in a ZeroDivisionError.

This fix adds a check to ensure the number of reviews is greater than zero before
performing the division. If there are no reviews, the average rating defaults to 0.0.

Author: Yosef-AlSabbah

shop/serializers.py

@@ -69,7 +69,10 @@ def get_rating(self, obj):
             cache.set(cache_key, cached_data, 604800)  # Cache for 1 week (604800 seconds)
         else:
             # Update cache incrementally
-            cached_data["average"] = cached_data["total_rating"] / cached_data["count"]
+            if cached_data["count"] > 0:
+                cached_data["average"] = cached_data["total_rating"] / cached_data["count"]
+            else:
+                cached_data["average"] = 0.0
 
         return {"average": cached_data["average"], "count": cached_data["count"]}