3.0.3 Support multiple discounts

[juanpprieto]

Add support for multiple discounts via addDiscount including tests.

Closes #1015

[Copilot]

Pull Request Overview

This PR adds support for multiple discount codes by updating the addDiscount functions in both the input mapper and checkout resource, along with corresponding tests. Key changes include reformatting conditional blocks for improved readability, modifying the addDiscount function to accept multiple discount codes, and updating the checkout resource to merge existing and new discount codes.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/input-map-resource.js	Reformatted conditionals and updated addDiscount to accept multiple discount codes.
src/checkout-resource.js	Refactored addDiscount to merge existing discount codes from different parts of the checkout object and adjusted other method invocations.
.changeset/ten-cooks-clap.md	Minor changeset update noting the support for multiple discounts.

Comments suppressed due to low confidence (1)

src/checkout-resource.js:209

• There is a typo in the variable name 'existtingLineCodes'. Consider renaming it to 'existingLineCodes' for clarity.

const existtingLineCodes = checkout.lineItems.map((lineItem) => {

[juanpprieto]

/snapit

[juanpprieto]

/snapit