Make geo-logcursor group configurable

What does this MR do?

Make geo-logcursor group configurable.

For example, you can already customize the owner of the geo-logcursor service by setting user['username'] = 'foo'.

This MR makes it so the group of geo-logcursor uses the setting user['group'] = 'bar'.

Related issues

• #7486 (closed)
• https://gitlab.com/gitlab-com/geo-customers/-/issues/119

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated - Mike: Do we need it for this?
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened

Test plan

Set user['group'] in gitlab.rb on a Geo secondary site, reconfigure, and see what group geo-logcursor service runs as.

If it's the specified group, then ✅. If it's git, then ❌.