Hook after change “Site Address (URL)” setting?

So, if you want to use your own domain on a WPMU subsite, you do three things. You change “Site Address (URL)” which chnages siteurl and home in the database, you park the domain on the web host so it recognises it, and you point your A record.

We will be managing multiple WPMUs with multiple subsites and the users will not have access to the web host control panel, so I would like to use their API to add the domain to the site as they change Site Address.

Is there such a hook? I can’t find one in site-info.php inside the block…
if ( isset( $_REQUEST['action'] ) && 'update-site' === $_REQUEST['action'] ) {
… but maybe there’s a general ‘change settings’ hook where you check for the setting after the hook? Somehow?

Thanks for any help all