curl --request GET \
  --url https://demo.onlinebillingform.com/api/v2/vpn/servers/list \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "vpn_systems": {
    "data": [],
    "current_page": 1,
    "last_page": 1,
    "per_page": 15,
    "total": 0
  }
}