There's no reason for this to be a category of error that emails the
server administrator, since there's a good chance that fixing it will
need to be done in the Zulip codebase, not administrator action.
This adds a new API for sending basic analytics data (number of users,
number of messages sent) from a Zulip server to the Zulip Cloud
central analytics database, which will make it possible for servers to
elect to have their usage numbers counted in published stats on the
size of the Zulip ecosystem.