Add a new type called UserSession and use it in the UserNav component

[jhodapp]

Description

This PR adds a new type called UserSession and uses it in the UserNav component.

GitHub Issue: None

Changes

• Add a new type called UserSession which holds more than just userId
• Use the new fields from the AuthStore in the UserNav component

Screenshots / Videos Showing UI Changes (if applicable)

Testing Strategy

1. Log in
2. View the UserNav menu (upper right hand corner menu)
3. Notice that the 2 letter icon is dynamically set to "FL" where FL == [F]irst + [L]ast
4. Notice that the user's full name is dynamically set
5. Notice that the user's email address is dynamically set

Concerns

None

[jhodapp]

Self-approving while David's fully occupied this week.