curl --request POST \
  --url https://openapi.enginy.ai/v1/lists/{listId}/contacts \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "contactIds": [
    123
  ]
}
'

{
  "status": "success",
  "message": "<string>",
  "data": {
    "requestedCount": 123,
    "addedCount": 123,
    "skippedCount": 123
  }
}