When a simple React context gets out of hand.

Description

Summary

• The AuthContext contains state associated with authentication.
• Both the AuthContext and TimelineContext are part of the global state so one solution would be to just combine them, and separate the domains inside the state object.
• Defining our initial state lets us see all of our global state at a glance.
• Now, we can set an initialSelectedPost & initialSelectedComment without worrying about the useEffect firing off;