curl --request POST \
  --url https://api.kapso.ai/platform/v1/whatsapp/broadcasts/{broadcast_id}/cancel \
  --header 'X-API-Key: <api-key>'

{
  "data": {
    "id": "5f6a7b8c-9d0e-1f2a-3b4c-5d6e7f8a9b0c",
    "status": "draft",
    "scheduled_at": null,
    "started_at": null,
    "completed_at": null
  }
}