curl -X GET "https://staging-api.loyalty.lt/en/shop/coupons/products?coupon_id=123" \
  -H "X-API-Key: your_api_key" \
  -H "X-API-Secret: your_api_secret"

{
  "success": true,
  "message": "Available products retrieved successfully",
  "data": {
    "products": [
      {
        "id": 1,
        "name": "Americano",
        "description": "Classic black coffee with hot water",
        "image_url": "https://example.com/images/americano.jpg",
        "sku": "COFFEE-001",
        "barcode": "4750000000001",
        "price": 2.90,
        "regular_price": 3.50,
        "currency": "EUR",
        "categories": [
          {
            "id": 1,
            "name": "Hot Drinks",
            "description": "Hot beverages"
          }
        ]
      },
      {
        "id": 2,
        "name": "Cappuccino",
        "description": "Espresso with steamed milk foam",
        "image_url": "https://example.com/images/cappuccino.jpg",
        "sku": "COFFEE-002",
        "barcode": "4750000000002",
        "price": 3.20,
        "regular_price": 3.90,
        "currency": "EUR",
        "categories": [
          {
            "id": 1,
            "name": "Hot Drinks",
            "description": "Hot beverages"
          }
        ]
      },
      {
        "id": 3,
        "name": "Latte",
        "description": "Espresso with steamed milk",
        "image_url": "https://example.com/images/latte.jpg",
        "sku": "COFFEE-003",
        "barcode": "4750000000003",
        "price": 3.50,
        "regular_price": 4.20,
        "currency": "EUR",
        "categories": [
          {
            "id": 1,
            "name": "Hot Drinks",
            "description": "Hot beverages"
          }
        ]
      }
    ],
    "total_count": 3,
    "selection_required": true
  }
}