curl --request GET \
  --url https://api.hyperline.co/v1/promotion-codes/{id} \
  --header 'Authorization: Bearer <token>'

{
  "id": "promo_DKL4Xcb5VSa8CQ",
  "code": "PROMO123",
  "coupon_id": "cou_DKL4Xcb5VSa8CQ",
  "client_id": "cli_DKL4Xcb5VSa8CQ",
  "customer_id": "cus_DKL4Xcb5VSa8CQ",
  "plan_id": "plan_DKL4Xcb5VSa8CQ",
  "product_id": "itm_DKL4Xcb5VSa8CQ",
  "created_at": "2021-01-01T00:00:00.000Z",
  "updated_at": "2021-01-01T00:00:00.000Z",
  "expires_at": "2021-01-01T00:00:00.000Z",
  "max_redemptions": 10,
  "current_redemptions": 0,
  "duration_count": 1,
  "duration_period": "months",
  "only_for_first_time_order": false
}