Fully functional attendance

[evan10s]

• Adds complete attendance flow
• Refactored navigation to use a SharedFlow and provide a better way to specify NavOptions
• Adds warning throughout app when the environment is not a production Apiary instance (closes #34)
• Fixes #38
• Closes #15

The list of things I fixed on this branch:

• [x] Pressing back on attendance screen after selecting an attendable should not go back to the attendable selection screen
• [x] Teams list needs polish and tabs for teams vs. events
• [x] After opening the app and before selecting an attendable, going to settings and back to the attendance tab causes a crash
• [x] Attendance screen needs polish and actual loading spinner during processing
• [x] Attendables list and attendance screen need error handling
• [x] Crash when unknown (to Apiary) GTID provided
• [x] Pressing Attendance in bottom nav while in attendance causes attendance screen to go blank

Despite all of the above, fixes #25

Closes #4 Closes #6

[kberzinch]

Looks good to me