List Open Loyalty rewards and let a member redeem one by spending points

Steps

1. GET /api/{storeCode}/reward to list the reward catalog, and GET /api/{storeCode}/member/{member} to check the member's current points balance.
2. POST /api/{storeCode}/reward/{reward}/buy with the member's customerId and any reward-type-specific fields (quantity, couponValue, withoutPoints, dateValid), since the request shape varies by reward type (static coupon, dynamic coupon, conversion coupon, material reward).
3. Handle documented error cases such as insufficient points or no coupons remaining in the reward's pool.
4. On success, retrieve the issued coupon using the returned issuedRewardId, or list it via the reward's coupon endpoint.
5. For campaign-driven free rewards, pass withoutPoints: true so points aren't deducted on redemption.