curl --request POST \
  --url https://demo.onlinebillingform.com/api/v2/customer/check \
  --header 'Content-Type: application/json' \
  --data '
{
  "username": "jsmith@example.com",
  "password": "<string>"
}
'

{
  "success": true,
  "user": {
    "id": 1,
    "name": "BillingServ Demo",
    "username": "admin",
    "email": "hello@baseserv.com",
    "account_type": 1,
    "live_api_token": "live_************************************"
  }
}