New response object: multicaixaExpress for QR code and deeplink payments

Multicaixa Express payments now return a multicaixaExpress object in the payment response, containing QR code and deeplink data to support the full checkout experience across desktop and mobile.

When brand is MULTICAIXAEXPRESS, the response includes:

Field	Type	Description
`deeplink`	string (uri)	Direct deeplink to open the Multicaixa Express app.
`deeplinkRedirect`	string (uri)	Redirect URL for browser and mobile flows to the app.
`qrCodeUrl`	string (uri)	URL of the QR code image.
`expiresAt`	string (ISO 8601)	Payment expiration timestamp.

{
  "multicaixaExpress": {
    "deeplink": "mcxwallet://purchase?qrref=...",
    "deeplinkRedirect": "https://api.sandbox.proxypay.co.ao/deeplink/...",
    "qrCodeUrl": "https://api.sandbox.proxypay.co.ao/qrcode/...",
    "expiresAt": "2026-05-22T19:14:04Z"
  }
}

On desktop, Paybyrd Checkout uses qrCodeUrl to display a QR code for the buyer to scan. On mobile, tapping Pay uses deeplinkRedirect to open the Multicaixa Express app directly.

See the Multicaixa Express guide and the Create Payment API reference for full details.