curl --request POST \
  --url https://api.useduro.com/v1/subscriptions/{id}/change-plan \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "planId": "<string>"
}
'

{
  "subscription": {
    "id": "<string>",
    "planId": "<string>",
    "currentPeriodStart": "<string>",
    "currentPeriodEnd": "<string>",
    "cyclesCompleted": 123,
    "createdAt": "<string>"
  },
  "proration": {
    "amount": 123
  }
}