Comment 2 for bug 1541173

I've pushed up a patch to disable the Persona auth plugin for new sites or upgrading sites where it is not yet in use (i.e. no auth instances of it).

I've also pushed up a separate patch that displays a warning message to the admin if the Persona plugin is enabled and/or in use. Since there is no existing Mahara API to show a custom message when a plugin is toggled from "disabled" to "enabled", I instead added it to the site_warnings() method that displays warnings on the Administration homepage.

I'm not sure if we actually want to start displaying that warning to admins yet, though, since we don't yet have a specific advisement for them about what they should do to migrate away.