curl --request POST \
  --url https://api.useduro.com/portal/email/subscriptions/{mode}/{id}/cancel \
  --header 'Content-Type: application/json' \
  --header 'x-portal-session: <api-key>' \
  --data '
{
  "atPeriodEnd": false
}
'

{
  "id": "<string>",
  "status": "<string>",
  "currentPeriodEnd": "<string>",
  "cancelAtPeriodEnd": true
}