Overview
To simplify work with orders, there exist several endpoints which allow to add/update/delete single orderItem instead of updating the whole order.
POST https://api.discover.swiss/test/market/v1/orders/{orderNumber}/items
PUT https://api.discover.swiss/test/market/v1/orders/{orderNumber}/items/{orderItemNumber}
DELETE https://api.discover.swiss/test/market/v1/orders/{orderNumber}/items/{orderItemNumber}
OrderItem model defintion: see here
Here is the list of operations you can do with order items: