[Spike] Investigate if user email can be consistently retrieved from GitHub

[yuvipanda]

Challenge admins often want (or need) to email signed up users for different reasons. Instead of having a separate profile form where users have to fill in their email, we should check to see if we can instead populate it directly from GitHub login.

Definition of done

• Investigate if email can be stored in the user model already
• If so, either simply change the default config we have so email is recorded, or refine an issue to do so if it is more complex than expected

Reference

user:email is a scope that's needed to ask for the User's email when logging in with GitHub (https://docs.github.com/en/apps/oauth-apps/building-oauth-apps/scopes-for-oauth-apps)