A store. Alias Tilttek\Progression\Store\ExperienceStore, MilestoneStore or StreakStore to your own
service; it must pass the library's contract test case.
A member's timezone.timezone_context reads it from the activity's context. To read it elsewhere — never from
something that changes after the gesture, or rebuilds give other days —, define the service
Tilttek\Progression\Streak\TimezoneResolver.
The observer. The projection and the keeper tell DispatchingObserver; listen to its events, or decorate it.
The tracks or the streaks. Replace the Tilttek\Progression\Tracks or Tilttek\Progression\Streak\StreakRules
service — from a database, for instance — and rebuild the projection when they change.
