https://www.geins.io/developers/how-to/add-product-to-cart
Add product to cart - Geins Commerce Backend
Add products to an existing cart using Geins Merchant API
cart geins commerceaddproduct
https://www.geins.io/developers/how-to/add-custom-data-to-cart
Add custom data to cart - Geins Commerce Backend
Learn how to add custom data to carts using Geins Merchant API
cart geins commerceadd custom
https://www.geins.io/developers/how-to/activate-promo-code
Activate promo code on cart - Geins Commerce Backend
Learn how to activate promo codes on carts using Geins Merchant API
cart geins commercepromo code