Fix for free shipping handling of minimum order rule

[anastas10s-afk]

Changes proposed in this Pull Request:

Fixes the calculation from when Apply minimum order rule before coupon discount is active and prices are entered inclusive of tax and displayed that way in cart and checkout, free shipping is no longer available (based on the minimum order amount including tax), as it uses the pre-tax amount when a coupon is applied.

Closes #28752 .

How to test the changes in this Pull Request:

Using the WooCommerce Testing Instructions Guide, include your detailed testing instructions:

1. Go to WooCommerce > Settings > Tax
2. Set Prices entered with tax to Yes, I will enter prices inclusive of tax
3. Set Display prices during cart and checkout to Including tax
4. Add a tax rate
5. Add Free shipping with a required minimum order amount
6. Check the Apply minimum order rule before coupon discount option for Free shipping
7. Add a physical product with a price inclusive of tax is above the minimum order amount, but the pre-tax amount is below the minimum order amount
8. Add a coupon that doesn't include free shipping
9. Add the product to the cart
10. Confirm free shipping is available
11. Add the coupon
12. Confirm free shipping is still available

[github-actions]

Hi ,

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[coreymckrill]

Thanks for the PR @anastas10s-afk !

👍 Tests well, although I think in the testing instructions, the last line would be clearer as "Confirm free shipping is still available".

[anastas10s-afk]

Thank you so much, @coreymckrill !
Plus, excellent remark on how the last line could be worded (It now reads as you suggested).

[fvdbgit]

@anastas10s-afk @coreymckrill : the changes do not work anymore with WooCommerce v8.0.2. In v8.0.2, when you add the coupon, the free shipping is not available anymore (on final step 12). Could you please check what happens? Thank you very much.

[coreymckrill]

Hi @fvdbgit, this fix is merged into trunk, but it hasn't been released yet. It should go out in the 8.1.0 release.