curl --request POST \
  --url https://api.example.com/api/Integrations/CampaignMonitor/Clients/{clientId}/Lists/{listId} \
  --header 'Content-Type: application/json' \
  --data '
[
  {
    "id": 123,
    "firstName": "<string>",
    "lastName": "<string>",
    "email": "<string>"
  }
]
'