Client and server both close the connection if they don't hear from the
other party after a timeout period. This is a failsafe and should
improve reliability.
Might not be necessary, but if it is then it prevents a sitation where a
websocket is still open but we've forgotten about it, so we will never
broadcast any new messages to it and the client will be practically frozen in
time until they disconnect and open a new websocket.
Also update the user's last_seen when the websocket is closed. This prevents a
user with js enabled who's actually idle being considered absent and being
rotated when their websocket accidentally closes for a few seconds.
Incoming requests are handled in anonstream/routes/. Route handlers
mainly depend on files in anonstream/, which in turn depend on files in
anonstream/helpers/ and anonstream/utils/. Utils are pure functions and
helpers are almost pure functions; they don't mutate state but they
do depend on the global app config.