SYS-674 helm chart updates for auth protection of mythtv-backend

[instantlinux]

Summary of Changes

• Simplify ingress definition for mythtv-backend helm chart
• Add more documentation around authentication of the setup dashboard

Why is this change being made?

When 35.0 came out a year ago, there was no way to secure the setup dashboard which had been combined into a single service on port 6544 with the old mythweb capability, which has been renamed "Web App". I submitted a request as issue #1077 for this capability, which until now has only been available for users of the pre-release 36.0 development branch.

Version 36.0 provides a username / password mechanism for protecting this service. By default, it's turned off. I've added documentation here to better explain how to set up this vital capability.

How was this tested? How can the reviewer verify your testing?

Local testing. I was unable to get Authelia's TOTP to behave quite right -- it works fine for applications that serve a login splash screen is served separately from the content, but I've never had luck configuring it for applications like this that bring up a username / password dialog box on the content page and use a separate URL for the http-POST login sequence. During testing I looked at unhelpful trace logs from authelia, searched high and low for anyone else using Authelia this way, and concluded that it's good enough for now to require separate authtotp login prior to accessing Myth Web App. This will need to be changed imminently anyway, as ingress-nginx is being retired by the Kubernetes project two months from now.

Completion checklist

• The pull request is linked to all related issues
• This change has unit test coverage
• Documentation has been updated
• Dependencies have been updated and verified