List all contacts

curl --request GET \
  --url https://api.caspen.com/v1/contacts

{
  "data": [
    {
      "id": "<string>",
      "type": "<string>",
      "title": "<string>",
      "first_name": "<string>",
      "last_name": "<string>",
      "preferred_name": "<string>",
      "profession": "<string>",
      "company": "<string>",
      "email": "<string>",
      "notes": "<string>",
      "phone_numbers": [
        {
          "id": "<string>",
          "code": "<string>",
          "number": "<string>",
          "type": "<string>"
        }
      ],
      "address": {
        "line1": "<string>",
        "line2": "<string>",
        "city": "<string>",
        "state": "<string>",
        "postal_code": "<string>",
        "country_code": "<string>"
      },
      "created_at": "<string>"
    }
  ],
  "links": {
    "prev": "<string>",
    "next": "<string>"
  }
}