curl --request GET \
  --url https://letterby.com/api/v4/audiences \
  --header 'apiKey: <api-key>'

{
  "data": {
    "audiences": [
      {
        "id": "<string>",
        "name": "<string>",
        "filters": "<string>",
        "mode": "smart",
        "listId": "<string>",
        "createdAt": "2023-11-07T05:31:56Z",
        "updatedAt": "2023-11-07T05:31:56Z",
        "subs": [
          {
            "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>"
          }
        ]
      }
    ]
  }
}