curl --request POST \
  --url https://api.unibee.dev/merchant/session/user_sub_update_url \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "cancelUrl": "<string>",
  "email": "<string>",
  "externalUserId": "<string>",
  "planId": 123,
  "productId": 123,
  "returnUrl": "<string>",
  "userId": 123,
  "vatCountryCode": "<string>"
}
'

{
  "code": 123,
  "data": {
    "url": "<string>"
  },
  "message": "<string>",
  "redirect": "<string>",
  "requestId": "<string>"
}