The doorkeeper redirects students away from course pages they're not supposed to see.
It's intended for use with Google Sites, and static sites posted on GitHub Pages, Netlify, and other stacking hosting servers.
It allows us to keep old course sites available to the students who enrolled in the respective offering, while reducing the chance that a current student will stumble across them, and making it marginally more difficult for someone to see material from a course they're not enrolled in.
This doesn't secure a website. A determined student can still hack their way into a site that the doorkeeper prevents.
yarn install
yarn serve
Visit http://localhost:5000. Use this to sign in and out of GitHub, and see whether you'd be able to see a website under different conditions.
cd functions
yarn shellyarn deploy
Add this to site pages:
<script src="olin-website-gatekeeper.firebase"></script>