curl --request POST \
  --url https://instance.prod.onboardapp.io/v1/cases/{case_token}/entities \
  --header 'Content-Type: application/json' \
  --header 'X-API-KEY: <api-key>' \
  --data '
{
  "entity_token": "<string>",
  "role": "Primary"
}
'

{
  "data": {
    "token": "ent_8f3k2m1n",
    "first_name": "John",
    "last_name": "Smith",
    "full_name": "John Smith",
    "company_name": "<string>",
    "date_of_birth": "2023-12-25",
    "nationality": "GB",
    "registration_number": "<string>",
    "country": "GB",
    "address": {
      "line1": "<string>",
      "line2": "<string>",
      "city": "<string>",
      "state": "<string>",
      "postal_code": "<string>",
      "country": "<string>"
    },
    "checks_summary": {
      "total": 123,
      "complete": 123,
      "pending": 123,
      "failed": 123
    },
    "alerts_summary": {
      "total": 123,
      "open": 123,
      "resolved": 123
    },
    "external_reference": "<string>",
    "created_at": "2023-11-07T05:31:56Z",
    "updated_at": "2023-11-07T05:31:56Z"
  },
  "meta": {
    "request_id": "req_9k4m2n1p3q",
    "page": {
      "cursor": "<string>",
      "has_more": true
    }
  }
}