A few specs in `dashboard_controller_spec.rb` set some state in redis but don't clean it up afterwards which causes other specs to fail when they're ran after `dashboard_controller_spec.rb`.
Related commit: 18467d4.
This commit adds a new notification that gets sent to admins when the site gets new features after an upgrade/deploy. Clicking on the notification takes the admin to the admin dashboard at `/admin` where they can see the new features under the "New Features" section.
Internal topic: t/87166.
