Richer reverse proxy authentication

Is your feature request related to a problem? Please describe.

Being able to use Authelia SSO without much fuss is great, but unfortunately the only piece of user information that recipes grabs right now is the HTTP_REMOTE_USER, which makes it hard to use the built in invite system!

Furthermore, the logout link is hard coded and cannot be overridden with an environment variable. This prevents being able to use an SSO logout url e.g. https://authelia.example.com/logout

Describe the solution you'd like

1. Add support for other header fields like:

• HTTP_REMOTE_NAME
• HTTP_REMOTE_EMAIL

2. Update this information as required when a user logs in e.g. their email address has changed.

3. Add an environmental variable REVERSE_PROXY_AUTH_LOGOUT to specify a custom logout URL.

Describe alternatives you've considered I guess I could manage users in Recipes as well as in Authelia, but that means double-handling of information for my use case.