curl --request POST \
  --url https://api.callers.ai/campaigns/{campaignId}/contacts/bulk \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "contacts": [
    {
      "name": "<string>",
      "phoneNumber": "<string>",
      "data": {},
      "phoneNumbers": [
        "<string>"
      ],
      "archived": false
    }
  ]
}
'

{
  "requested": 123,
  "added": 123,
  "modified": 123,
  "contactIds": [
    "<string>"
  ]
}