We don't want to depend on:
1) socket.io generated IDs because they change on server reconnect
2) simple-peer generated IDs because they change for every peer
connection
We generate a single ID when the call web page is refreshed and use that
throughout the session (until page refresh).
We keep relations of user-id to socket-id on the server side in memory
and use that to get to the right socket. In the future this might be
replaced with Redis to allow multiple nodes.
If the server is restarted, but people have active calls, we want them
to keep using the active peer connections and only connect to new peers.
Ideally, we do not want to disturb the active peer connections, but peer
connections might be restarted because the in-memory store will not have
the information on for any peers in the room upon restart.
Pug contains a lot of unnecessary dependencies leading to code bloat,
which results in increased docker package size, and thus docker image
size). express-dot-engine is much simpler and performs better.
This should not cause compile issues when simple-peer is not installed
(because client-side JS will be precompiled after pkg is published in
NPM repository) because types are not used in runtime.
