**What**
- Ensure that swaps can be created for orders with discounts in tax inclusive regions
**How**
- Retrieve cart with discounts and region before creating adjustments for line items in cart.
- In `discountService.calculateDiscountForLineItem` we used the method `totalsService.getLineItemTotals` if a line-item is tax inclusive. This method uses some fields from the cart that aren't populated on cart creation (such a `items` which caused the original error).
**Testing**
- add integration test `swaps > tax inclusive > "Complete swap flow with discount"` that creates a swap in the following environment
- tax inclusive region
- tax inclusive line item to be swapped
- fixed type discount with allocation: total
Fixes CORE-748
15d6f92964