Add spam detection in case a user copy/pastes a hyperlink to everybody
on chat via their DMs:
* If the same link is copied to many different people within a time
window, the user can be kicked from the chat room with a warning.
* The server remembers rate limits by username, so if they log back in
and continue to spam the same links, they instead receive a temporary
chat ban.
* The spam threshold, time window and ban hours are configurable in the
BareRTC settings.toml.
Other fixes:
* The front-end will send a "me" update with its current status and
video setting in the 'onLoggedIn' handler. This should help alleviate
rough server reboots when a ton of idle users are online, so they
don't spam "me" updates to correct their status once the WhoLists
begin to roll in.
