curl --request POST \
  --url https://verification.didit.me/v3/billing/top-up/ \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "amount_in_dollars": 51,
  "success_url": "<string>",
  "cancel_url": "<string>"
}
'

{
  "checkout_session_id": "<string>",
  "checkout_session_url": "<string>"
}