curl --request POST \
  --url https://api.example.com/sync/init \
  --header 'Content-Type: application/json' \
  --data '
{
  "token": "<string>",
  "password": "<string>",
  "machine_id": "<string>",
  "sync_interval_secs": 123
}
'

{
  "success": true,
  "is_new_user": true,
  "machine_id": "<string>"
}