Just need to send messages into rooms now for a first cut to be done. Notable
improvements to make:
- We currently do 1 goroutine per service. This could be bad if we have lots of these things running around.
- We do not cache the response to RSS feeds. If we have 10 independent services on the same feed URL, we will
hit the URL 10 times. This is similar to how we currently do 1 webhook/service, so it's plausible that in
the future we will want to have some kind of generic caching layer.
- We don't send messages to Matrix yet. We need a `Clients` instance but can't get at one. There's only ever
one, so I wonder if we should global it like we do with `GetServiceDB()` for ease of use?
- The polling interval is divorced from the actual feed repoll time. Ideally we would schedule the goroutine
only when we need it, rather than checking frequently, determining we have nothing to do, and going back
to sleep.