curl -X PATCH "https://gateway.jelou.ai/ecommerce/v2/apps/{app_id}/coupons/{coupon_id}" \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Black Friday 30%",
    "discount_value": 30,
    "valid_until": "2026-12-02T23:59:59Z"
  }'

{
  "data": {
    "id": "9e3f2c1a-8b7d-4e6f-a5c4-d3b2a1e0f9c8",
    "code": "BLACKFRIDAY25",
    "name": "Black Friday 30%",
    "description": "25% off the entire store",
    "discount_type": "percentage",
    "discount_value": "30.000000",
    "status": true,
    "valid_from": "2026-11-25T00:00:00.000000Z",
    "valid_until": "2026-12-02T23:59:59.000000Z",
    "max_uses": 100,
    "once_per_client": true,
    "applies_to_all_branches": true,
    "state": "scheduled",
    "created_at": "2026-07-02T15:30:00.000000Z",
    "updated_at": "2026-07-02T16:00:00.000000Z"
  }
}