Add support for Bacs Direct Debit payment method

[asumaran]

Closes #3751

Changes proposed in this Pull Request:

Enable checkout using Bacs Direct Debit between merchants and customers in the UK.

Testing instructions

Important

To enable Bacs Direct Debit as a payment method option, you must first activate it using the following feature flag:wp option update _wcstripe_feature_lpm_bacs 'yes'.

Important

(assuming you are receiving webhook events correctly) – After completing the checkout and receiving the initial webhook events from Stripe, to speed up order processing, you need to manually run the scheduled action. To do this, go to Tools > Scheduled Actions, search for the wc_stripe_deferred_webhook hook, and click "Run". After this, the order status should change to “Processing.”

Checkout using Bacs with a simple product

• Switch to this branch: as-bacs.
• Add a simple product to the cart.
• Go to the Checkout page.
• Enter a UK billing address.
• Select “Bacs Direct Debit” from the list of payment methods.
• Use the sort code “10-88-00” and account number “00012345”.
• Check “I understand that Stripe will be collecting…”.
• Click “Place Order”.
• You should be redirected to the "Order received" page.
• Verify the order status changes to "Processing" after some time.

Checkout using Bacs with a virtual product.

• Follow the same steps as in the previous block, but this time add a virtual product to the cart instead of a simple product.

Verify that Bacs is not displayed as an option if the feature flag is set to no.

• Run wp option update _wcstripe_feature_lpm_bacs 'no'
• Add a simple product and go to the checkout page. Bacs should no longer be available as a payment option.
• Go to the Stripe settings page. Bacs should no longer be available as a payment option.

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• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[asumaran]

@rafaelzaleski Please hold off on reviewing this PR for now. I’m currently investigating an issue I just discovered.

[asumaran]

False alarm. I thought the payment method was supposed to disappear when entering a billing address from an unsupported country. I could have sworn it worked that way while working on the spike. However, the payment method only disappears after entering the address and refreshing the page. I tested with another similar payment method (Cash App), and the behavior is the same, so it’s not a bug. Please review @rafaelzaleski

[rafaelzaleski]

Looks good and tests well! I only left a minor request for changes related to i18n.

[rafaelzaleski]

@asumaran, there are also failing unit tests related to the changes in this branch.

[asumaran]

@rafaelzaleski I'll take a look at those.