Install prebuilt Redis and cmark-gfm from APT

This brings GitLab CI run duration down from 11 minutes to 9 minutes.

• Install Redis from official Redis APT repo, instead of compile
• Install cmark-gfm from Debian APT repo, instead of compile
• Change Java installation to headless, sufficient for html5validator

mentioned in commit c5a62dfe

merged

When I was setting up the testing server I didn't realize this but installing Redis via apt may have introduced an issue with 2 Redis services trying to run at the same time. Since we create a service unit and I guess the Redis from apt also creates one?

It's possible that specifically the Hetzner Debian 12 repositories include a service file in one of their Redis packages but not the Vagrant ones, that might explain why it doesn't happen in Vagrant.

In any case I fixed it by stopping and disabling the other unit so not really a big problem.

That's interesting. I guess I should add an Ansible step to stop and disable any existing service, before adding the custom one. At least on Red Hat, /etc/systemd/system takes precedence over /usr/lib/systemd/system. Assume true on Debian too.

- name: Stop and disable the redis-server service that gets installed somewhere
  ansible.builtin.systemd_service:
    name: redis-server
    state: stopped
    enabled: false

This worked for me though I don't know if this would error out if the redis-server service doesn't exist. Maybe it needs an ignore_errors: true too.

mentioned in merge request !11 (merged)

mentioned in commit tildes/tildes@72b6c60a

mentioned in commit tildes/tildes@65bf6af1