Enhanced handling of large quantities in the Carts API update endpoint

When handling requests with exceptionally large quantities (exceeding 1,000,000), the update endpoint of the Carts API previously capped the value to 1,000,000 and returned a 200/OK status without notifying the user.

We have now modified this behavior. While the update endpoint will continue to limit the quantity to 1,000,000, it will also issue a 422/Unprocessable Entity status alerting the API users to the adjustment.

The endpoint will not perform any additional quantity checks against inventory levels; this aspect remains consistent with previous functionality.