[ADD] ecommerce: new payment providers page

Adding a documentation on payment providers specifically for the
ecommerce section.

closes odoo/documentation#3521

Taskid: 3138597
X-original-commit: 6b45da21c1
Signed-off-by: Aarab Tom (toaa) <toaa@odoo.com>

content/applications/websites/ecommerce/checkout_payment_shipping.rst

@@ -7,3 +7,4 @@ Checkout, payment, and shipping
 
    checkout_payment_shipping/cart
    checkout_payment_shipping/checkout
+   checkout_payment_shipping/payments

content/applications/websites/ecommerce/checkout_payment_shipping/payments.rst

@@ -0,0 +1,34 @@
+=================
+Payment providers
+=================
+
+Odoo supports a multitude of online
+:doc:`payment providers </applications/finance/payment_providers>` for your website, allowing your
+customers to pay with their preferred payment methods.
+
+Configuration
+-------------
+
+To set up payment providers on the eCommerce app, go to :menuselection:`Website --> Configuration
+--> Payment Providers`. From here, :guilabel:`Activate` the payment providers you wish to have
+available on your shop, and configure them according to your needs.
+
+Alternatively, you can access **payment providers** via :menuselection:`Website --> Configuration
+--> Settings`. In the :guilabel:`Shop - Payment` section, you can :guilabel:`Configure SEPA Direct
+Debit` if you wish to use it, as well as :guilabel:`View other providers`. If you use the
+:guilabel:`Authorize.net` payment provider, the
+:ref:`Payment Capture Method <payment_providers/features/manual_capture>` can be configured in that
+same menu.
+
+If you are using :doc:`/applications/finance/payment_providers/paypal`, you can also enable and
+configure it here.
+
+Checkout payment options
+------------------------
+
+Once activated, customers can choose the payment provider of their choice during the **checkout
+process**, at the :guilabel:`Confirm Order` step.
+
+.. image:: payments/payments-checkout.png
+   :align: center
+   :alt: Payment provider selection at checkout