Decouple 'accounts' from the registration/login process

[porowns]

In order to enable other authentication methods like SSO logins from Discord, we need to decouple the user CRUD process from the login/logout/register process.

auth_extensions

• Covers login, register, logout
• Email activation

user_extensions

• Covers setting values on the Django User object (username, email, password)
• Covers UserInfo profiles

This way, we can swap out auth_extensions for something like discord SSO, and users will be able to set up their profile and information without being dependent on some arbitrary auth process.