curl --request POST \
  --url https://api.example.com/v1/sdk/activate \
  --header 'Content-Type: application/json' \
  --data '
{
  "customerRef": "<string>",
  "planRef": "<string>",
  "productRef": "<string>"
}
'

{
  "checkoutSessionId": "<string>",
  "checkoutUrl": "<string>",
  "creditBalance": 123,
  "creditsPerUnit": 123,
  "currency": "<string>",
  "message": "<string>",
  "purchaseRef": "<string>"
}