Now zero dollar subscriptions won't trigger renawal emails anymore

[leonardola]

Fixes https://github.com/woocommerce/woocommerce-subscriptions/issues/4778

Description

This PR adds a check to prevent sending renewal reminders for 0 dollar orders

How to test this PR

• Checkout to this PR's branch
• Place a subscription order
• Go to /wp-admin > WooCommerce > Subscriptions > Edit
• Make sure the Send upcoming renewal notification option does not show up in the order actions select box
• Change the next renewal to happen in just a few minutes from now
• Wait until the renewal happens
• Make sure you don't receive a Manual renewal notice email but you do receive a Thank you for your order email

Product impact

• Added changelog entry (or does not apply)
• Will this PR affect WooCommerce Subscriptions? yes/no/tbc, add issue ref
• Will this PR affect WooCommerce Payments? yes/no/tbc, add issue ref
• Added deprecated functions, hooks or classes to the spreadsheet

[james-allan]

Changes look good.

• I confirmed that the action is removed for free subscriptions.

trunk	This branch

• I confirmed that subscriptions with a recurring total still include the action and it still works (ie sends the email).
• Confirmed that subscriptions with a recurring total still sends the email via AS. *
• Confirmed that free subscriptions don't send the email via AS. *

* To test the emails are and aren't sent in a normal scenario I used this code snippet to simulate a renewal that is due in 3 days + 10 seconds. ie the email should send in 10 seconds.

wcs_get_subscription( 466 )->update_dates( [
	'next_payment' => gmdate( 'Y-m-d H:i:s', time() + ( 3 * DAY_IN_SECONDS ) + 10 ),
] );

I left a small comment about the changelog entry.

[ebinnion]

Out of curiosity, why <= 0? Is there ever a case where we have a negative subscription? And if so, is that a refund? And if so, should we break?

[leonardola]

Out of curiosity, why <= 0? Is there ever a case where we have a negative subscription?

The only way for the subscription totals to be negative in that flow is if the merchant sets a bigger discount than the product price in the admin area and then select Send upcoming renewal notification and click update order.

And if so, is that a refund?

Subscriptions can't really be refunded what gets refunded are orders and orders don't have the Send upcoming renewal notification option so that flow would never run when refunding.

I've also tested coupons and they only discount up to 100% of the cart/order total.
Even products with negative price end up creating a subscriptions with a $0 total though the order has a negative total