* zulip: Treat unknown errors with a 10-second backoff.
An unknown error (including an unauthorized error) would fall through
with no calls to time.Sleep, resulting in hammering the server as
quickly as possible.
Add a 10-second sleep in the default error case. The heartbeat is
left with no explicit sleep, but all other codepaths now contain one.
* version: Move version information into a separate package.
This will allow it to be accessed by other sections of the code.
* zulip: Use the matterbridge version in the user-agent.
Co-authored-by: Wim <wim@42.be>
