curl --request GET \
  --url https://api.salesbricks.com/api/v2/subscriptions/{subscription_id}/upgrade \
  --header 'X-SALESBRICKS-KEY: <api-key>'

{
  "orders": [
    {
      "order_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
    }
  ]
}