Replace hardcoded feed names in class-rewrite with actual feeds

[gsusI]

Fixes issue: #21373

Context

Summary

This PR can be summarized in the following changelog entry:

• Improves compatibility with custom RSS feeds. Props to @gsusI.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• add the following snippet to your theme's functions.php:

add_action( 'init', 'twentytwentyfour_pattern_categories' );


function add_custom_feed() {
	add_feed('custom', 'do_feed_rss2');
}

add_action( 'init', 'add_custom_feed' );

• visit Settings > Permalinks and save to flush the rewrite rules
• visit the Yoast SEO settings, Category section, then disable Show the categories prefix in the slug and save
• pick a category, e.g. basic.wordpress.test/catname/
• try to visit the related custom feed e.g. basic.wordpress.test/catname/custom/
  • Without this PR you should get an error like "The site cannot be reached"
  • With this PR you should not get an error and you should see/download a RSS feed.

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes #21373

[josevarghese]

Development team kindly please check the comment from the user at here: #21373 (comment)

[enricobattocchi]

Hey @gsusI, thanks for the patch! It will be part of an upcoming release.