Install Janus config files from TinyPilot Debian package

[mtlynch]

Blocked on https://github.com/tiny-pilot/tinypilot-pro/pull/985

We're currently placing Janus' config files using Ansible:

tinypilot/ansible-role-ustreamer/tasks/install_janus.yml

Lines 21 to 32 in d903d32

	- name: create Janus config files
	template:
	src: "{{ item }}.j2"
	dest: "{{ ustreamer_janus_configs_dir }}/{{ item }}"
	owner: root
	group: root
	mode: "0644"
	loop:
	- janus.jcfg
	- janus.transport.websockets.jcfg
	notify:
	- restart Janus

It should be trivial to pull this logic out of Ansible and implement it instead in TinyPilot's Debian package.

Some notes on the migration:

• The Ansible task is a template task even though the source files don't have any templated values. I don't know if this was a mistake originally or if they used to have templates, but now they're just static files.
  • This makes the task easier, as we should be able to move the files like this:
    • ansible-role-ustreamer/templates/janus.jcfg.j2 -> debian-pkg/etc/janus/janus.jcfg
    • ansible-role-ustreamer/templates/janus.transport.websockets.jcfg.j2 -> debian-pkg/etc/janus/janus.transport.websockets.jcfg
• The Ansible task templatizes the path based on ustreamer_janus_configs_dir, but we can hardcode the path to /etc/janus for simplicity.
• We don't have to implement logic for restarting the Janus service.
• We should preserve root as the user and group.
• We should preserve 0644 as the permissions, but if that generates a CI error in lintian, we should accept lintian's suggestion. The important thing is that the execute bit is off for everyone and the write bit is off for non-owner.

Similar work

• Install lib/usb-gadget.sh via Debian package #1412

[jdeanwallace]

@mtlynch - Is this a duplicate of tiny-pilot/ustreamer-debian#12?

Do we want to configure Janus in the TinyPilot or uStreamer Debian package?

[mtlynch]

Do we want to configure Janus in the TinyPilot or uStreamer Debian package?

I'd like to do it in the TinyPilot Debian package because then it's all in a single repo. It's maybe more logical from the uStreamer Debian package, but then we're spreading more of our code across repos, which I think outweighs other concerns.

[mtlynch]

@db39 - Can you take this on next? This one is similar in process to #1467 but the process is simpler because we can do everything in a single change to the tinypilot repo rather than bouncing between this repo and the ustreamer-debian repo.

[db39]

• We should preserve root as the user and group.
• We should preserve 0644 as the permissions, but if that generates a CI error in lintian, we should accept lintian's suggestion. The important thing is that the execute bit is off for everyone and the write bit is off for non-owner.

For handling these permissions, should I use tinypilot.postinst to set them?

[mtlynch]

@db39 - I don't think we should have to explicitly set the permissions in postinst. I think apt-get just copies over the files with the right permissions, but double check after installing.