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

{
  "data": {
    "audience": {
      "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>"
        }
      ]
    }
  }
}