* Fix up some comments to match other comments in the WC code base
* Add some missing esc_* functions
* Add a gateway filter to get_customer_tokens + a test for it
* Added comment to `get_icon` method
* Added missing return tag to `is_available` method
* Fix return type typo `wp_error => WP_Error`
* Renamed integer to int
For Subscriptions v2.0.
* Use new 'woocommerce_subscription_failing_payment_method_updated_' hook
* Use new wcs_is_subscription() method to run process_subscription() when the
transaction is for a subscription object.
* Save the card and customer IDs on the 'shop_subscription' post from the renewal
order rather than saving it on the order which purchased the subscription.
* Add new save_subscription_meta() method to allow us to save customer ID both
in Subscriptions 1.n on the original order and in 2.0 on the subscription/s
created for the order)
* Use the new 'woocommerce_scheduled_subscription_payment_simplify' hook and
deprecate use of the old 'scheduled_subscription_payment_simplify' hook by
moving it to the WC_Addons_Gateway_Simplify_Commerce_Deprecated class
* Use core WC methods on the renewal order passed to scheduled_subscription_payment()
to process the payment rather than having to call special Subscriptions API methods
like WC_Subscriptions_Manager::process_subscription_payments_on_order() and
WC_Subscriptions_Manager::process_subscription_payment_failure_on_order()
* Use the original order's total to determine the amount to charge up-front to
save having to call WC_Subscriptions_Order::get_total_initial_payment()
* Use a description for recurring payments that is consistent with standard orders,
i.e. "{Site Name} - Order {order_id}" instead of a description that does not include
the renewal order's ID. This helps link payments to orders (which can then be traced
to subscription/s).
So that if the renewal is for a failed payment, the the new value is set
on the renewal order's `'_simplify_customer_id'` post meta value and can
be copied back to the original order in `update_failing_payment_method()`.
Mike Jolley
Claudio Sanches
James Koster
Justin Shreve
Fredrik Forsmo
Mehdi Esmaeili
roykho
Brent Shepherd
George Stephanis
Ben Bidner
Danny van Kooten
Nicola Mustone
John Clause
Paul Wilde