Updates for sign up demo

[erikguntner]

Closes #replace_this_text_with_the_issue_number

What changes did you make?

• Saving the user to the database when they are invited by a coordinator.
• Updated the /new-password endpoint to retrieve the user from the db after updating their password and add id_token to the new session cookie.
• Updated the User type on the front end to contain a UserRole type.
• Added functionality to redirect the user to the correct homepage based on role after signing in.
• Moved the logic to log in with OAuth to a custom hook.
• Generated temporary passwords to be sent when a user is invited.

Testing done for these changes

• I went through the sign up flows for coordinators, hosts, and guests multiple times in both a staging and development environment.