curl --request POST \
  --url https://app.dynamicauth.com/api/v0/environments/{environmentId}/custom/hostnames \
  --header 'Content-Type: application/json' \
  --data '{
  "hostname": "auth.dynamic.xyz",
  "usage": "cookies"
}'

{
  "id": "95b11417-f18f-457f-8804-68e361f9164f",
  "hostname": "auth.dynamic.xyz",
  "usage": "cookies",
  "status": "active",
  "verificationRecords": [
    {
      "dnsRecordType": "TXT",
      "verificationType": "certificate",
      "name": "<string>",
      "value": "<string>"
    }
  ],
  "errors": "<string>"
}