The `non_archived` scope applied here
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/controllers/conc
erns/issues_action.rb#L5 overrides the previous `ORDER BY` applied
inside the IssuesFinder, with the default scope of the Project model,
resulting in SQL errors.

Prevent Groups to have smaller visibility than projects
Add default_group_visibility_level to configuration
Code improvements

The route is supposed to redirect the Groups#index request based on
whether or not a user was logged in. If they are, we redirect them to
their groups dashboard; if they're not, we redirect them to the public
Explore page.

But due to overly aggressive `before_action`s that weren't excluding the
`index` action, the request always resulted in a 404, whether a user was
logged in or not.

Closes #12660