* fix: normalize cart json utf8 and add tests
Ensure cart and checkout responses are cleaned to valid UTF-8 before JSON encoding and cover Utf8Cleaner with unit tests.
Made-with: Cursor
* fix: normalize order response to valid UTF-8 before JSON encoding
- Add Utf8Cleaner::clean() for successful order creation response (data)
- Add Utf8Cleaner::clean() for validation error response (ErrorBag)
- Prevents Malformed UTF-8 characters error when creating order with
non-UTF-8 data from OpenCart/DB (same approach as cart endpoints)
Made-with: Cursor
Nikita Kiselev
f894d33c46