curl --request POST \
  --url https://api.hubapi.com/marketing/campaigns/2026-03 \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "properties": {}
}
'

{
  "businessUnits": [
    {
      "id": 123
    }
  ],
  "createdAt": "2023-11-07T05:31:56Z",
  "id": "<string>",
  "properties": {},
  "updatedAt": "2023-11-07T05:31:56Z"
}