curl --request POST \
  --url https://api.hubapi.com/engagements/v1/engagements \
  --header 'Content-Type: application/json' \
  --data '
{
  "engagement": {
    "type": "EMAIL",
    "active": true,
    "ownerId": 123,
    "timestamp": 123
  },
  "associations": {
    "contactIds": [
      123
    ],
    "companyIds": [
      123
    ],
    "dealIds": [
      123
    ],
    "ownerIds": [
      123
    ],
    "ticketIds": [
      123
    ]
  },
  "attachments": [
    {
      "id": 123
    }
  ],
  "metadata": {}
}
'

{
  "engagement": {},
  "associations": {},
  "attachments": [
    {}
  ],
  "metadata": {}
}