Allows the partner to update the quantities for order items. The endpoint accepts amendments for multiple items in a single
call. It is recommended that the integrating partner batches all the substitutions for an order in a single call
of this endpoint in order to avoid receiving a rate limit exceeded error.
- Order has to be in the 'PLACED' status in order to successfully process this request.
- An item (identified by id) can be amended only once.
- The final_quantity value has to be less than the original quantity value.
- Unchanged items are not allowed in the request.