curl --request POST \
  --url https://letterby.com/api/v4/contacts \
  --header 'Content-Type: application/json' \
  --header 'apiKey: <api-key>' \
  --data '
{
  "email": "<string>",
  "listId": "<string>",
  "firstName": "<string>",
  "lastName": "<string>",
  "phoneNumber": "<string>",
  "data": {},
  "address": "<string>",
  "isGDPR": true,
  "name": "<string>",
  "instagram": "<string>",
  "twitter": "<string>",
  "website": "<string>",
  "company": "<string>",
  "country": "<string>",
  "city": "<string>",
  "sendVerificationEmail": true
}
'

{
  "data": {
    "contact": {
      "id": "<string>",
      "email": "<string>",
      "firstName": "<string>",
      "lastName": "<string>",
      "phoneNumber": "<string>",
      "createdAt": "2023-11-07T05:31:56Z",
      "points": 123,
      "referrals": 123,
      "listId": "<string>",
      "isVerified": true,
      "unsubscribed": true,
      "data": {},
      "address": "<string>",
      "isGDPR": true,
      "name": "<string>",
      "instagram": "<string>",
      "twitter": "<string>",
      "website": "<string>",
      "company": "<string>",
      "country": "<string>",
      "city": "<string>",
      "list": {
        "id": "<string>",
        "name": "<string>",
        "url": "<string>",
        "mode": "<string>",
        "referrals": true,
        "color": "<string>",
        "title": "<string>",
        "desc": "<string>"
      },
      "audiences": "<array>",
      "referralLink": "<string>",
      "privateLink": "<string>",
      "position": 123
    }
  }
}