Add a supporting code to separate groups#show
and groups#details which is required for the
proper implementation of the Group Overview
content and Security Dashboard option for it

- we now use the hierarchy class also for epics
- also rename supports_nested_groups? into supports_nested_objects?
  - move it to a concern

With this MR, group clusters is now functional, so default to enabled.

Have a single setting on the root ancestor group to enabled or disable
group clusters feature as a whole

Mayra Cabrera authored 6 years ago and Thong Kuah committed 6 years ago

As the frontend is still in progress and other related backend is still
in prgress we need a feature flag to turn off Group Clusters.

As this is the only item in this menu, make Kubernetes the link for the
sidebar item too.

Sam Beckham authored 6 years ago and Olivier Gonzalez committed 6 years ago

- Allow to extend nav links for the Group sidebar

Partially addresses #47424.

This allows us to check specific abilities in views, while still
enabling/disabling them at once.

Previously, these wouldn't count issues or MRs in subgroups - meaning that if
_this_ group had no issues or MRs, we'd show the empty state, which was wrong.

Tests for these new helper methods

Closes #37745

…based on whether the current user owns the parent group and whether the parent group or current group is share locked.

fixed up Ruby based on review

fixed some more breadcrumb titles