Applies a promotion discount code to the cart. The code is matched case-insensitively.
For gift cards, use the dedicated POST /carts/{cart_id}/gift_cards endpoint instead.
Publishable API key for store access
JWT token for authenticated customers
Bearer token for authenticated customers
Order token for guest access
Unique key for request idempotency.
Cart prefixed ID (e.g., cart_abc123)
Promotion discount code to apply
"SAVE10"
discount code applied