Add filter for express checkout address normalization

[daledupreez]

Fixes STRIPE-824
Fixes #4819

Changes proposed in this Pull Request:

This PR implements a new wc_stripe_express_checkout_normalize_address filter that runs as part of our existing wc_stripe_normalize_address AJAX action that normalizes addresses for express checkout. This will allow for additional normalization of address data for express checkouts.

Testing instructions

Start with inspection. You can also verify that the hook is running and would be used by doing the following:

• Set up a Stripe test site using the code from this branch
• Ensure that you have an express checkout payment method enabled
• Ensure that logging for Stripe is enabled
• Add the following snippet to log the data from the filter:

function test_express_checkout_address_filter( $normalized_data, $original_data ) {
	WC_Stripe_Logger::debug( 'debug address filter', [ 'normalized_data' => $normalized_data, 'original_data' => $original_data ] );
	return $normalized_data;
}
add_filter( 'wc_stripe_express_checkout_normalize_address', 'test_express_checkout_address_filter', 10, 2 );

• Add a product to your cart and use an express checkout method to make the purchase
• After completing the purchase, verify that you're getting the data in your debug log from the filter

Note: I tried to write unit tests, but the fact that ajax_normalize_address() uses filter_input() means we can't mock the data in $_POST.

---

• Covered with tests (or have a good reason not to test in description ☝️)
• [N/A] Tested on mobile (or does not apply)

Changelog entry

• This Pull Request does not require a changelog entry. (Comment required below)

Changelog Entry Comment

Comment

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)

[Copilot]

Pull request overview

This PR adds a new WordPress filter wc_stripe_express_checkout_normalize_address that allows developers to customize address normalization for express checkout payment methods (Apple Pay, Google Pay, etc.). The filter is applied after WooCommerce Stripe's built-in normalization logic, enabling additional address data transformations as needed by merchants or extensions.

• Introduces the wc_stripe_express_checkout_normalize_address filter in the AJAX address normalization handler
• Provides access to both normalized and original address data for flexible customization
• Updates changelog and readme to document the new filter

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
includes/payment-methods/class-wc-stripe-express-checkout-ajax-handler.php	Adds the new filter after existing normalization methods, providing normalized and original address data as parameters
readme.txt	Documents the new filter addition in the changelog section
changelog.txt	Documents the new filter addition in the current version's changelog

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[wjrosa]

Looks good to me! I would consider Copilot's suggestion

[diegocurbelo]

LGTM, and it tests as indicated.