Secure Payment Confirmation

Pay $0.01 will make the following request with a nonexistent credential:

new PaymentRequest([{
  supportedMethods: 'secure-payment-confirmation',
  data: {
    credentialIds: [Uint8Array.from(
        atob(window.localStorage.getItem('no_credential_identifier')),
        c => c.charCodeAt(0))],
    instrument: {
      displayName: 'Bob Pay',
      icon: 'https://rsolomakhin.github.io/pr/spc-no-credential/bobpaycc.png',
    },
    challenge: textEncoder.encode('challenge'),
    timeout: 60000,
    payeeOrigin: window.location.origin,
  },
}], {
  total: {
    label: 'Total',
    amount: {
      currency: 'USD',
      value: '0.01',
    },
  },
});

Based on the Secure Payment Confirmation explainer.