There are site settings here which have been added in previous versions, we need to deprecate the site settings in this version and then remove them in the next version. We have a SiteSetting::DeprecatedSettings class to do this.
Also renaming site settings in migrations will result in the “old” site settings being reset to their default values until the latest code is deployed. Even if we move this to a post migration, the “new” site settings will have the default values until the migration runs.
O this is tricky… deprecating site settings just prevents undefined method errors in case plugins are using them. It doesn’t help to prevent the window where site settings get reset to their default values. We need to think about how to close that window.
Yes we need to keep this, because onebox HTML structure is stored in post cooked content. We will need a full rebake before we can remove this. (Or a DB migration to find/replace cooked… but that sounds very risky)