This fixes an issue where the topic invitation rate limiter
for invites for the 1 minute period was incorrectly using
1 day as the length of time the limit should be applied over.
The default for `max_topic_invitations_per_minute` is 5,
so this would be very easy to exceed, then the user gets
a very confusing warning message saying they have to wait
23 hours to send more invites.
This commit also makes other `RateLimiter` period parameters
more consistent by always using the form `N.PERIOD` instead
of things like `86_400` hardcoded seconds per day.
ec7c6b1f96