Protect some MyST pages with authorization (authentication, password, etc)

[choldgraf]

MyST sites for communities may have a combination of content that is available to the public, as well as content that is only meant for the team. For sites that are in private repositories, we could allow communities to maintain both types of content in a single repository, and allow readers access via a lightweight security measure like a password.

This would probably only work in the context of a MyST server, but a very lightweight implementation could still go a long way.

Ideas for ways to protect some pages

• Passwords: The simplest thing would be to define a simple password in the page metadata so that the rendered version gives a password prompt before displaying.
• User authentication: A better case would be if users could bring authentication with them somehow, for example with a jupyterhub or another auth provider, and those credentials would be used to give access after a one-time sign-in.