Create new endpoint for getting available pages to be manually selected for llms.txt

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Uses indexables for populating the dropdowns for the manual page selection in llms.txt.

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:

• Confirm you have indexables enabled and the SEO optimization completed
• Go to yoast settings->llms.txt
• Click on a dropdown and confirm that you see the 10 most recently modified public pages to select.
• If you write something in the dropdown, confirm that you see the pages that are properly filtered by what you wrote. The thing you wrote filters page titles.
• Select one page, save, refresh and confirm that it persists
• From the 10 most recently modified public pages that you saw in the previous steps, change some of them likeso:
  • Make one private
  • Make one draft
  • Make one scheduled
  • Make one noindexed
  • Make one password-protected
• Revisit the llms.txt settings page and this time when you click on a dropdown you see again the 10 most recently modified pages, but you won't see the ones you edited in the previous step
• Repeat the above tests, for when you have reset and disabled indexables. (the only difference is that the noindexed page will still appear in the dropdown.

Error handling:

• You have to use POSTMAN for this, as there's no easy way to trigger an error here
  • As usual, use this post, to be able to authenticate your request there
• Do a GET request to /wp-json/yoast/v1/available_posts and confirm you get data for pages
• Do a GET request to /wp-json/yoast/v1/available_posts?postType=post and confirm you get data for posts
• Do a GET request to /wp-json/yoast/v1/available_posts?postType=NOT_VALID_POST_TYPE and confirm you get a 400 response with the "error": "The post type asked is not valid" body

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:

• With indexables both enabled and disabled (and reset), confirm that llms.txt file stays the same both with this RC/PR and without.

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 #

[coveralls]

Pull Request Test Coverage Report for Build df3ee4c37827f5029be50fd71f4b65ab2e8cd5eb

Details

• 9 of 109 (8.26%) changed or added relevant lines in 10 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.4%) to 53.618%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/repositories/indexable-repository.php	2	3	66.67%
src/llms-txt/domain/available-posts/invalid-post-type-exception.php	0	2	0.0%
src/conditionals/llms-txt-enabled-conditional.php	0	4	0.0%
src/llms-txt/infrastructure/content/automatic-post-collection.php	5	9	55.56%
src/llms-txt/domain/content-types/content-type-entry.php	2	8	25.0%
src/llms-txt/domain/available-posts/data-provider/parameters.php	0	7	0.0%
src/llms-txt/application/available-posts/available-posts-repository.php	0	8	0.0%
src/llms-txt/domain/available-posts/data-provider/available-posts-data.php	0	8	0.0%
src/llms-txt/domain/available-posts/data-provider/data-container.php	0	11	0.0%
src/llms-txt/user-interface/available-posts-route.php	0	49	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/llms-txt/domain/content-types/content-type-entry.php	2	37.5%

Totals
Change from base Build 3345d606d20f13b8d77cb46181044002eb00136e:	0.4%
Covered Lines:	30493
Relevant Lines:	57870

---

💛 - Coveralls

[github-actions]

A merge conflict has been detected for the proposed code changes in this PR. Please resolve the conflict by either rebasing the PR or merging in changes from the base branch.

[thijsoo]

CR + ACC 👍

One thing I did notice is that the get pages request is fired everytime you hit the page. Which we will solve in a different issue