Constructor
# new UserInteractionManager()
Methods
# areDifferent()
Returns true if the two passed arrays (of strings) are different in some way.
# buildASnapshot()
Create and return a snapshot data structure.
# dailyUpdate()
Once a day, update the snapshot, and generate UserInteraction documents as appropriate.
# initialize()
Build and save an in-memory snapshot. Run at system startup time.
# setVisibility()
Returns an array of strings indicating the current visibilities for the user.