wp_replace_insecure_home_url()
Replaces insecure HTTP URLs to the site in the given content, if configured to do so.
WordPress File wp-includes/https-migration.php
wp_should_replace_insecure_home_url()
Checks whether WordPress should replace old HTTP URLs to the site with their HTTPS counterpart.
wp_update_https_migration_required()
Updates the ‘https_migration_required’ option if needed when the given URL has been updated from HTTP to HTTPS.
wp_update_urls_to_https()
Update the ‘home’ and ‘siteurl’ option to use the HTTPS variant of their URL.
wp_should_replace_insecure_home_url
Filters whether WordPress should replace old HTTP URLs to the site with their HTTPS counterpart.