* Trying some models for audience segmentation
* AudienceSegment basics
* Attach AudienceSegment to DisplayAd
* Possibly use a DUS to populate AudienceSegments
* Add to display ad form UI
* Add to display ad API
* Refresh strategy for audience segments
* Add user_id to async ads query
* Maybe :testing -> :manual, for no-refresh segment
* Test & tweak segment refresh
* Testing audience_segment#refresh logic
* Coverage: testing human_readable
* Scope segment refresh to recently active users
* Tweak logic for when to refresh
* Tweak experience levels to match SettingsHelper
* Test for front-end logic
* Fix test, hope this helps coverage?
* Better test names
* One worker for all, many workers for each, perform_bulk
* Fix audience segment UI, needs to use id, not enum
* cron/schedule should RefreshAll
* Singular id in RefreshWorker
