curl --request POST \
  --url https://api.useduro.com/portal/email/wallet/topup \
  --header 'Content-Type: application/json' \
  --header 'x-portal-session: <api-key>' \
  --data '{
  "amount": 5000
}'

{
  "checkoutToken": "<string>",
  "checkoutUrl": "<string>"
}