This is a feature that used to be present in discourse-assign but is
much easier to implement in core. It also allows a topic to be assigned
without it claiming for review and vice versa and allows it to work with
category group reviewers.
Sometimes you want stale data right away, then refresh it async.
This adds `findStale` to the store for that case. If it returns
an object with `hasResults` you can get the `results` and display
them.
It also returns a `refresh()` method to freshen up the stale data.
To enable `localStorage` support for stale data, just include the
mixin `StaleLocalStorage` into an adapter for that model. This
commit includes a sample of doing that for `Notifications`.
