fix(serializer): fallback on utf-8 decoder error

Author: hassiebp

langfuse/serializer.py

@@ -75,7 +75,10 @@ def default(self, obj: Any):
                 return str(obj)
 
             if isinstance(obj, bytes):
-                return obj.decode("utf-8")
+                try:
+                    return obj.decode("utf-8")
+                except UnicodeDecodeError:
+                    return "<not serializable bytes>"
 
             if isinstance(obj, (date)):
                 return obj.isoformat()