const url = 'https://api.gnosispay.com/api/v1/auth/nonce';
const options = {method: 'GET', body: undefined};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}

"a1b2c3d4e5f6"