- jz.bm.realtime-access admits holders of jz.bm.access_materials
(Assumption A5), so every editor can follow materials:{id}
- README documents the materials channel, event and authorizer
jz.bm.realtime-access admits chat-group members and, through
golem15.presentations' owner guard, presentation owners; everyone else
gets 401, 403 or 503 with Cache-Control no-cache, private. /_chat,
/_chatchannels and /_chatbots are reserved for the APIs.
