Route macros for the two board admin pages: the list (/admin/boards) and a
single board (/admin/boards/:id). Returned from
PhoenixKitBoards.route_module/0; PhoenixKit injects these inside the admin
live_session (auth + admin layout applied automatically).
Both localized (/:locale/admin/...) and non-localized sets are defined, as
required — each route needs a unique :as.