Improve out-of-the-box experience when invoking web UI container

[Martchus]

• Configure a default certificate in the container startup
  script (as a fallback)
• Start and configure the database inside the container unless
  the database has been configured by the user manually
• Improve documentation
• See https://progress.opensuse.org/issues/127091
• See https://progress.opensuse.org/issues/127139

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching docs/*.asciidoc:

• Consider generating documentation locally to verify it is rendered correctly using tools/generate-htmldoc

This is an automatically generated QA checklist based on modified files.

[Martchus]

Note that I've simply tested this by building the container image locally via podman image build --tag openqa_webui_local_build . and then using openqa_webui_local_build:latest instead of registry.opensuse.org/devel/openqa/containers15.4/openqa_webui:latest.

We have tests for the docker-compose setup which shouldn't be impacted by this.

I'm still getting the error Can not create MOJO_TMPDIR : mkdir /var/lib/openqa/share/factory: File exists at /usr/share/openqa/script/../lib/OpenQA/Setup.pm line 337. which I'm going to look into but this error was there before and shouldn't prevent use to merge this.

[kalikiana]

Nice. I can confirm that it works now.

[Martchus]

Looks like codecov hasn't run at all. Since I'm not changing any Perl code anyways I'm just merging the PR manually.