curl -X GET \
  'https://api.appcharge.com/coupons/coupon/summer26' \
  -H 'x-publisher-token: <x-publisher-token>'

{
    "name": "summer26",
    "active": true,
    "discountPercentage": 10,
    "maxRedemptionsPerCustomer": 2,
    "expiredBy": "2025-04-02T06:54:51.670Z",
    "startsAt": "2025-02-02T06:54:51.670Z",
    "supportedOfferExternalIds": ["bundle1", "rollingoffer3"],
    "firstTimePurchase": false,
    "allowedPlayers": ["player123", "player456", "player789"]
}

{
    "error": "Invalid coupon name. Use only English letters and numbers."
}

{
    "error": "Coupon not found."
}

{
    "error": "Unexpected error. Please contact support."
}