Identity Service contains all the information related to user state,
addresses and keys.
This patch also introduces the `State` type which can be used by other
services to maintain their own copy of this state to avoid lock
contention.
Finally, there are currently no external facing methods via a CPC
interface. Those will added as needed once the refactoring of the
architecture is complete.
This patch adds the User Event Service which is meant to replace the
current event polling flow.
Each user interested in receiving events should register a new
subscriber using the `Service.Subscribe` function and then react on
the incoming events.
The current patch does not hook this up Bridge user as there are no
existing consumers, but it does provide extensive testing for the
expected behavior.
