It could be nice to have a "code" or "key" field for userBroadcasts collection to have easier relationship with such an announcement to users and the origin of the announcement itself.
In our context, announcement are created in relationship with a specific event (a maintenance or whatever). Have a dedicated field to identify it afterwise in the list would be great benefit (we could have many planned in quite limited period of time) instead of looking at hours or detals of each to identify the right looked-up one.
Moreover, as such announcements are created by REST calls from ou maintenance scheduler, it will increase loose coopling between both, as the former one would be able to lookup by its own key in Syracuse in case of update (or whatever) instead of having to collect and save the $uuid.