Add BECS Debit support for tokenization

[rafaelzaleski]

Closes #3965

Changes proposed in this Pull Request:

• Make AU BECS Debit reusable and introduce tokenization.
• Enhance unit test coverage for BECS Debit.

Testing instructions

Use the following bank account for testing:

BSB: 000-000
Account Number: 000123456

• Store currency needs to be AUD.
• Stripe Account should be located in Australia.

Test 1: Add, Remove and Mark the token as default in the my account page.

1. Log in as a customer.
2. Go to My Account > Payment methods.
3. Add a new payment method and select “BECS Direct Debit”
4. After successfully adding the BECS payment method, verify it shows up under Payment methods.
5. Remove the BECS payment method by clicking “Delete” and confirm the token is removed.
6. Add the BECS payment method again and a credit card payment option, then mark BECS as default by selecting “Make default.” Confirm it is set as the default payment method.

Test 2: Save the token at checkout, and use the saved token in a subsequent purchase.

1. Add a product to your cart and proceed to checkout.
2. In the Payment section, choose “BECS Direct Debit.”

• Ensure there’s an option like “Save this payment method”, select it.

3. Enter the required bank details (test routing and account numbers) and complete the checkout.
4. After the order is placed, verify the order confirmation and note that a new BECS token should be created for your account.
5. Start a new purchase (add another product to cart).
6. At checkout, select the saved BECS token.
7. Complete checkout without having to re-enter bank account details. Confirm the purchase is successful and uses the existing BECS token.
8. Repeat for the shortcode and blocks checkout.
9. Go to My Account > Payment methods and confirm the tokens created in this test are present.

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

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• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
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[ricardo]

LGTM and tests well, nice work!

I left 2 questions about the payment method display being inconsistent between My account and checkout, but otherwise everything is looking good.

• ✅ Test 1: Add, Remove and Mark the token as default in the my account page.
• ✅ Test 2: Save the token at checkout, and use the saved token in a subsequent purchase.
  • Note: Tested on blocks and checkout.

[ricardo]

Should this be "BECS Direct Debit ending in %s" ?

[ricardo]

In the payment methods listing it appears like this for me:

Becs Direct Debit ending in 3456

Is it possible to enforce the capitalization for the method brand?