Add current_quantity to IOrderLineItem inteface

[peter-visualsquares]

The current_quantity field is added in api version 2024-01 https://shopify.dev/changelog/addition-of-lineitem-current_quantity-on-admin-rest-api

The field is optional because some older api version (e.g. 2023-10) does not have it.

[coveralls]

coverage: 100.0%. remained the same when pulling b7690af039b809d101194cb33221bbbebbe2af09 on peter-visualsquares:peter-0001-add-current-quantity-to-line-item into 19916ac257e106431bf1ec5b5951f68e2665a44c on MONEI:master.

[lpinca]

Thank you.