Volume discounts using Shopify Storefront API

[Sarthakrakhra]

Hey all!

We have a custom web-app which is using Shopify as a backend. We are taking advantage of the Checkout resource from the Storefront API in our front-end to make our cart page function. 

When the user submits the details on the cart page we pass the Checkout ID to our custom backend, create a draft-order out of that, do some further processing, and complete the draft-order to create a real order. Here we use the Shopify REST APIs. 

The issue we are facing now is that we would like to apply volume discounts (discounts based on quantity of certain line items), but are not seeing any solution to do that through the Checkout resource through the Storefront API. Are there any resources we could look at to help us achieve this?