curl --request POST \
  --url https://api.example.com/v1/billing/checkout-session \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "tier": "<string>",
  "interval": "<string>"
}
'

{
  "session_id": "<string>",
  "checkout_url": "<string>",
  "product_id": "<string>",
  "expires_at": "2023-11-07T05:31:56Z"
}