Switching a WordPress site from HTTP to HTTPS has historically been a tedious task. While on the surface the Site Address and WordPress Address have to be updated, existing content still remains using HTTP URLs where hard-coded in the database. Furthermore, updating _two_ URLs to migrate to HTTPS is still a fairly unintuitive step which is not clearly explained.
This changeset simplifies migration from HTTP to HTTPS and, where possible, makes it a one-click interaction.
* Automatically replace insecure versions of the Site Address (`home_url()`) with its HTTPS counterpart on the fly if the site has been migrated from HTTP to HTTPS. This is accomplished by introducing a `https_migration_required` option and enabling it when the `home_url()` is accordingly changed.
* A new `wp_replace_insecure_home_url()` function is hooked into various pieces of content to replace URLs accordingly.
* The migration only kicks in when the Site Address (`home_url()`) and WordPress Address (`site_url()`) match, which is the widely common case. Configurations where these differ are often maintained by more advanced users, where this migration routine would be less essential - something to potentially iterate on in the future though.
* The migration does not actually update content in the database. More savvy users that prefer to do that can prevent the migration logic from running by either deleting the `https_migration_required` option or using the new `wp_should_replace_insecure_home_url` filter.
* For fresh sites that do not have any content yet at the point of changing the URLs to HTTPS, the migration will also be skipped since it would not be relevant.
* Expose a primary action in the Site Health recommendation, if HTTPS is already supported by the environment, built on top of the HTTPS detection mechanism from [49904]. When clicked, the default behavior is to update `home_url()` and `site_url()` in one go to their HTTPS counterpart.
* A new `wp_update_urls_to_https()` function takes care of the update routine.
* A new `update_https` meta capability is introduced to control access.
* If the site's URLs are controlled by constants, this update is not automatically possible, so in these scenarios the user is informed about that in the HTTPS status check in Site Health.
* Allow hosting providers to modify the URLs linked to in the HTTPS status check in Site Health, similar to how that is possible for the URLs around updating the PHP version.
* A `WP_UPDATE_HTTPS_URL` environment variable or `wp_update_https_url` filter can be used to provide a custom URL with guidance about updating the site to use HTTPS.
* A `WP_DIRECT_UPDATE_HTTPS_URL` environment variable or `wp_direct_update_https_url` filter can be used to provide a custom URL for the primary CTA to update the site to use HTTPS.
Props flixos90, timothyblynjacobs.
Fixes#51437.
Built from https://develop.svn.wordpress.org/trunk@50131
git-svn-id: http://core.svn.wordpress.org/trunk@49810 1a063a9b-81f0-0310-95a4-ce76da25c4cd
