curl --request POST \
  --url https://api.scribe-mail.com/v1/smart_fields \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "smart_field": {
    "label": "<string>",
    "required": true,
    "integration_id": "<string>",
    "integration_attribute": "<string>"
  }
}
'

{
  "data": {
    "id": "<string>",
    "label": "<string>",
    "slug": "<string>",
    "required": true,
    "default": true,
    "position": 123,
    "integration_id": "<string>",
    "integration_attribute": "<string>",
    "used_in_signatures": true,
    "created_at": "2023-11-07T05:31:56Z",
    "updated_at": "2023-11-07T05:31:56Z"
  }
}