Sign via app

See a sample process flow as below:

1. Homepage, click GrabPay to add payment.	2. Click on ADD payment methods.	3. Click Alipay as method.
4. System will invoke Alipay wallet and redirect to Sign page. Click to confirm the sign.	5. Key in the payment password to confirm the sign.	6. Successfully returned from Alipay wallet.
7. 3rd Party App deducts money via payment interface