The core/hub class and related code, has a lot of deprecated methods that are due for removal. These were deprecated in the first place when the original "hub" functionality that existed on the old moodle.net was removed. These now need to be cleaned up and the class itself likely refactored.

We should also look to see if the `registration_hubs` table needs to still exist or if it can be deprecated too. We still need to store the registration status of the site, but I also don't think we need a dedicated table for it