If no `from` param is specified we calculate and use the "current
token" that inlcuded typing, presence, etc. These are unused during
pagination and are not available on workers, so we simply don't
calculate them.
Currently when fetching state groups from the data store we make two
hits two the database: once for members and once for non-members (unless
request is filtered to one or the other). This adds needless load to the
datbase, so this PR refactors the lookup to make only a single database
hit.
don't filter membership events based on history visibility
as we will already have filtered the messages in the timeline, and state events
are always visible.
and because @erikjohnston said so.
