Add Card Onsite payment method

[jimmyn]

Instead of redirecting the customer to MONEI's payment page, we should display the Card Input and Cardholder name fields directly on the checkout page.

Integration docs: https://docs.monei.com/docs/integrations/build-custom-checkout/ How to send cardholder name: https://docs.monei.com/docs/guides/send-cardholder-name/

Here is the example of similar Magento integration

Magento Demo: https://magento2-demo.monei.com/

• [ ] Add Card Input Component
• [ ] Add Cardholder Name field
• [ ] Add frontend validation for both fields
• [ ] Confirm payment using monei.confirmPayment without redirect
• [ ] Add an option in admin to switch between Onsite and Redirect integrations