Fix: Facet returns no result for a term having accent characters

[burhandodhy]

Description of the Change

This PR fixes the issue where the facet returns no result for a term having accent characters

Closes #3023

How to test the Change

• Create a new category غير-مصنف
• Assign some posts to new category
• Go to frontend and select غير-مصنف from taxonomy widget
• EP should returns the from غير-مصنف category

Changelog Entry

Fixed - Facet returns no result for a term having accent characters

Credits

Props @burhandodhy

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.

[felipeelia]

Facets e2e tests are consistently failing in this one @burhandodhy. Do you mind giving a look before we merge it? Thanks!

[burhandodhy]

Facets e2e tests are consistently failing in this one @burhandodhy. Do you mind giving a look before we merge it? Thanks!

@felipeelia Tests are fixed. The problem was that the sanitize_title function was not a good choice for meta fields and sanitize_text_field for taxonomies. So to fix the problem, I introduced the new method sanitize_callback in classes. Now every class will have the ability to change the satanize function without effecting the other classes.

[felipeelia]

@burhandodhy after giving this one a deeper look, it seems we might be going in the wrong direction. Instead of fixing the sanitization of the slug, your new code actually showed me we have a different problem:

If we create a post with a meta field with that same value, the meta facet will generate a URL with a different value than the taxonomy:

https://ep-es7.test/?ep_filter_category=%25d8%25ba%25d9%258a%25d8%25b1-%25d9%2585%25d8%25b5%25d9%2586%25d9%2581&ep_meta_filter_my_first_field=%D8%BA%D9%8A%D8%B1-%D9%85%D8%B5%D9%86%D9%81 (see how ep_filter_category is different from ep_meta_filter_my_first_field but they should be the same.)

Investigating it a little bit, it seems things work well if we use $term->name instead of $term->slug. Do you mind giving it another look? Feel free to ping me on slack to discuss the best way to move forward.

[felipeelia]

@burhandodhy great progress on this one, thanks. I've left yet another comments/suggestions/changes here, let me know your thoughts about it.
One thing that I'm trying to do is to add unit tests for all filters/actions being called. Do you think it would be possible to add unit tests for these new filters as well? Thanks!

ps.: there is also a conflict with the facets e2e tests, if you don't mind fixing it.

[burhandodhy]

@felipeelia I made the changes that you requested. I also added the tests for the filters.

[felipeelia]

We are almost there, @burhandodhy!

[felipeelia]

Thanks for all the hard work on this one @burhandodhy!