Renegotiation is not correct when the stream is fresh, for example
after the user has switched the camera.

Otherwise the callbacks don't get set.

Closing the channel could cause a panic if a c.write was pending.
Instead, ensure we send a closeMessage to the writer, and cause the
writer to exit when it receives a closeMessage.

We used to silently fail when there was a problem with camera
permissions.  Display a notification.

Thanks to Ines Klimann.

In current versions of pion, SetRemoteDescription fails if ICE is
currently gathering.  Work around the issue by resetting the connection.

This will hopefully become unnecessary once we have better congestion
control.

JSDoc doesn't recognise them otherwise.

Thanks to Rémi Nollet and Léo Stefanesco.

For now, join must follow login, but it will make it easier to extend
the protocol for joining multiple groups (think federation).

No need to carry password around.

More reliable reaction to network failures when they are detected
by just one side.