Improve discounts integration with cart transformations

[a47ae]

We're currently using a cart transform expand operation to add fees to cart items in Shopify. This operation expands each item into two components: the original item and the associated fee. However, we've encountered an issue with how discounts are applied in this scenario.

Current Behavior
Discounts are only applied to the bundle parent product, affecting the combined price (item + fee) instead of just the item price.

Example:
We have a line item in the cart with Product A. We then expand this into Product A and Fee B. No if the customer applies a discount for 10 %, valid for Product A, the following calculation happens

(`Product A - price` + `Fee B - price`) * 0,9

our desired Behavior would be

(`Product A - price` * 0,9) + `Fee B - price`

The problem could potentially be solved by:

• Gaining access to discounts which will be applied to a line item within the cart transform function
  • This would allow us to increase the price of the fee to compensate the discount
• Implementing logic for discounts to operate only on bundle children
  • Probably this is out of scope for the functions team, but it would be neat to allow merchants to apply discounts on a bundle component basis
• Changing the order of operations (applying discounts before cart transformation)
  • If the discounts would be applied before the cart transformation this could also be solved

[andrewchen5678]

Hit the same issue today