Support public/no-auth Library-backed sites

[afischer]

Problem Description

A number of users have wanted to use Library as a CMS for a site open to the internet. While we do not "officially" support this setup, it can be done by overriding authentication in the app.

Feature

We should support, through an environment variable or otherwise, the ability to generate a "public" library site. When in this state

• No authentication is required to view the content of the site
• The site should not show the user banner
• All edit buttons should be hidden

Additional Information

Possible features

• Allow authentication to show edit buttons