* Add instance-expose-public-timeline flag
Adds a config flag that allows unauthenticated access to /api/v1/timelines/public. Defaults to false to replicate existing behaviour.
* Update structure following review
* Add comment
* Fix linting
* start moving some database stuff around
* continue moving db stuff around
* more fiddling
* more updates
* and some more
* and yet more
* i broke SOMETHING but what, it's a mystery
* tidy up
* vendor ttlcache
* use ttlcache
* fix up some tests
* rename some stuff
* little reminder
* some more updates