const response = await fetch(
  'https://service.pcibooking.net/api/payments/paycard/2821a46d80e14d1b96a7f18f1b81926d/users',
  {
    headers: {
      'Authorization': 'APIKEY your-api-key'
    }
  }
);

const data = await response.json();
console.log(data);

import requests

response = requests.get(
    'https://service.pcibooking.net/api/payments/paycard/2821a46d80e14d1b96a7f18f1b81926d/users',
    headers={'Authorization': 'APIKEY your-api-key'}
)

print(response.json())

[
    "tpPMiFSB"
]

{
    "code": -1003,
    "message": "Not authorized to access this resource",
    "moreInfo": "Bad or missing authorization data, expected APIKEY",
    "errorList": null
}