curl --request POST \
  --url https://api.youka.io/api/v1/billing/checkout \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "productType": "subscription",
  "quantity": 123,
  "platform": "api",
  "cycle": "monthly"
}
'

{
  "url": "<string>",
  "sessionId": "<string>"
}