Custom Content Types: Ensure settings page functionality works without module requirement

[coder-karen]

Fixes https://github.com/Automattic/vulcan/issues/508

Proposed changes:

This PR ensures the Custom Content Types card with Jetpack Portfolio and Testimonials toggles and links on the Jetpack > Settings > Writing page can continue to function when there is no Custom Content Types module file in Jetpack. This is because this file will be removed as part of the cleanup once the Classic Theme Helper plugin is live and the features loaded via the Classic Theme Helper package directly.
Changes include:

• The creation of a new REST API route, which allows information about the Custom Content Type to be passed (name, status, whether it is overridden). This also allows values to be overridden by third parties.
• There is also a window variable fallback with an initial value, following the same style as other initial states such as JP_CONNECTION_INITIAL_STATE. This prevents delayed loading of the custom content type settings card by using the value directly, instead of waiting for the rest_api_init hook.
• On the React writing page itself, instead of checking for the module we check that the Custom Content Type status is active, before showing the card.
• I've removed Custom Content Types from the legacy Jetpack modules page - /wp-admin/admin.php?page=jetpack_modules - rather than trying to create a workaround. It also it wasn't working prior to this PR.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• On the Jetpack Settings > Writing page, make sure there is a settings card showing for Custom Content Types. Toggle testimonials and portfolios on and off, checking the following:
  • When toggling either on, you should see the 'portfolio' or 'testimonial' text in the description has now become a link, and clicking on it opens the page to add a portfolio or testimonial. The 'Add a testimonial' or 'Add a portfolio' link should also be added underneath the toggle, and the link should work.
  • When toggling either on, the menu item should display, and the feature should be enabled or disabled as expected.
  • Clicking on 'learn more' and the privacy info link via the info icon should continue to work.
  • Search for 'Testimonials' or 'Portfolios' via the Search box, and it should show the Custom Content Types section.

This functionality should continue to work both with and without the Custom Content Types module file in place. However if you want to test that removing the module file also does not break any functionality, then delete the jetpack/modules/custom-content-types.php file and follow the same testing steps as above.

[github-actions]

Thank you for your PR!

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[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the remove/custom-content-type-module-requirement branch.

  • For jetpack-mu-wpcom changes, also add define( 'JETPACK_MU_WPCOM_LOAD_VIA_BETA_PLUGIN', true ); to your wp-config.php file.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack remove/custom-content-type-module-requirement
  

  bin/jetpack-downloader test jetpack-mu-wpcom-plugin remove/custom-content-type-module-requirement
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2