// Create a payment invoice
const response = await fetch('https://api.nirapay.com/v1/invoices', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    amount: 100,
    currency: 'USDT',
    description: 'Order #1234',
    webhook_url: 'https://yoursite.com/webhook',
  }),
});

const invoice = await response.json();
// { id: 'inv_xxx', payment_url: 'https://pay.nirapay.com/...' }