[Issue #3244] auth login home and error redirects

[doug-s-nava]

Summary

Fixes #3244

Time to review: 10 mins

Changes proposed

• the callback route, which previously routed to the User page for all cases with different string messages, will now redirect to the home page on success, or an unauthorized page if no token is present or error page in error cases
• created error and unauthorized pages
• added middleware to implement the correct status codes on these redirects

Note that the error handling here is temporary for phase one, we will revisit as per this ticket for the next phase #3341

Context for reviewers

Testing steps

1. start with npm run dev on this branch
2. visit http://localhost:3000?_ff=authOn:true and log in
3. VERIFY: on successful login you're returned to the home page
4. visit htp://localhost:3000/api/auth/callback (note no token is present)
5. VERIFY: you're redirected to the unauthorized page
6. simulate an error by throwing from line 12 of the callback route
7. attempt login
8. VERIFY: you're redirected to the error page

Additional information

Screenshots, GIF demos, code examples or output to help show the changes working as expected.

[acouch]

👍🏿