const subscribeToBackInStock = async (variantId, phoneNumber, countryName) => {
  const response = await fetch('https://app.getwax.io/public_api/back_in_stock_subscriptions', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      back_in_stock_subscription: {
        shopify_product_variant_id: variantId,
        contact_phone_number: phoneNumber, // Recommended format: "33624682446"
        contact_country: countryName // Full country name in English
      }
    })
  });
};