Commerce Stripe: Payment Request Button

Integration of payment request button from Stripe as payment provider.
https://stripe.com/docs/stripe-js/elements/payment-request-button

With this module your customers can use apple pay, google pay, microsoft pay on your site.
Module adds a BUY button on cart page depending on device and browser, users can click and use Apple, Google or Microsoft pay. This payment gateway uses custom checkout flow and skips most of the regular steps.

Prerequisites
Before you start testing this payment, you need to:
- Add a payment method to your browser. For example, you can save a card in Chrome, or add a card to your Wallet for Safari.
- Serve your application over HTTPS. This is a requirement both in development and in production. One way to get up and running locally is to use a service like ngrok to set up an SSH tunnel.
- Locally also use https://www.drupal.org/project/ngrok_drupal to have sessions working (logging in, carts etc)
- Register your domain with Apple Pay, both in development and production. https://dashboard.stripe.com/account/apple_pay

REQUIREMENTS
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Stripe PHP library and JS stripe elements library, Stripe PHP is included via composer, stripe elements JS is loaded remotly

INSTALLATION
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Enable module, go into admin/commerce/config/payment-gateways and enable already added "Commerce Stripe - payment request button"
payment.

CONFIGURATION
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Once you enable payment gateway as described above, add publishable and secret key

Decoupled (Headless) Support
This module has decoupled (headless) support with Stipe JS SDK.
If you have a complex multi currency setup , then it is also possible to set the exact config in the order state.
The key name the module expects is "stripe_payment_request_button_config_id"
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2.x uses Payment Intent API (has 3DS in it), while 1.x uses old Charges API