Move group "Administration" nav behind feature flag

There has been some negative feedback about how this may be confusing.
Reverting docs and moving behind a feature flag till we can determine
how to move forward.

app/helpers/groups_helper.rb

@@ -10,7 +10,7 @@ module GroupsHelper
     ]
   end
 
-  def group_nav_link_paths
+  def group_settings_nav_link_paths
     %w[
       groups#projects
       groups#edit

app/views/layouts/nav/sidebar/_group.html.haml

@@ -133,7 +133,7 @@
                   = _('Members')
 
       - if group_sidebar_link?(:settings)
-        = nav_link(path: group_nav_link_paths) do
+        = nav_link(path: group_settings_nav_link_paths) do
           = link_to edit_group_path(@group) do
             .nav-icon-container
               = sprite_icon('settings')

ee/app/helpers/ee/groups_helper.rb

@@ -11,10 +11,22 @@ module EE
         .count
     end
 
-    def group_administration_nav_link_paths
+    def group_nav_link_paths
       %w[saml_providers#show usage_quotas#index billings#index]
     end
 
+    def group_settings_nav_link_paths
+      if ::Feature.disabled?(:group_administration_nav_item, @group)
+        super + group_nav_link_paths
+      else
+        super
+      end
+    end
+
+    def group_administration_nav_link_paths
+      group_nav_link_paths
+    end
+
     def size_limit_message_for_group(group)
       show_lfs = group.lfs_enabled? ? 'and their respective LFS files' : ''
 
@@ -91,7 +103,9 @@ module EE
     end
 
     def show_administration_nav?(group)
-      group.parent.nil? && can?(current_user, :admin_group, @group)
+      ::Feature.enabled?(:group_administration_nav_item, group) &&
+      group.parent.nil? &&
+      can?(current_user, :admin_group, group)
     end
 
     def administration_nav_path(group)

ee/app/views/groups/ee/_settings_nav.html.haml

+- administration_nav_item_disabled = Feature.disabled?(:group_administration_nav_item, @group)
+
 - if Gitlab::Auth::Ldap::Config.group_sync_enabled? && can?(current_user, :admin_ldap_group_links, @group)
   = nav_link(path: 'ldap_group_links#index') do
     = link_to group_ldap_group_links_path(@group), title: 'LDAP Group', class: 'qa-ldap-synchronization-link' do
       %span
         LDAP Synchronization
 
+- if show_saml_in_sidebar?(@group) && administration_nav_item_disabled
+  = nav_link(path: 'saml_providers#show') do
+    = link_to group_saml_providers_path(@group), title: _('SAML SSO'), data: { qa_selector: 'group_saml_sso_link' } do
+      %span
+        = _('SAML SSO')
+
 - if @group.feature_available?(:group_webhooks) || show_promotions?
   = nav_link(path: 'hooks#index') do
     = link_to group_hooks_path(@group), title: 'Webhooks' do
@@ -15,3 +23,15 @@
     = link_to group_audit_events_path(@group), title: 'Audit Events', data: { qa_selector: 'audit_events_settings_link' } do
       %span
         Audit Events
+
+- if show_usage_quotas_in_sidebar? && @group.parent.nil? && administration_nav_item_disabled
+  = nav_link(path: 'usage_quotas#index') do
+    = link_to group_usage_quotas_path(@group), title: s_('UsageQuota|Usage Quotas') do
+      %span
+        = s_('UsageQuota|Usage Quotas')
+
+- if show_billing_in_sidebar? && administration_nav_item_disabled
+  = nav_link(path: 'billings#index') do
+    = link_to group_billings_path(@group), title: _('Billing') do
+      %span
+        = _('Billing')

ee/spec/helpers/ee/groups_helper_spec.rb

@@ -233,6 +233,16 @@ describe GroupsHelper do
 
         expect(helper.show_administration_nav?(subgroup)).to be false
       end
+
+      context 'when `group_administration_nav_item` feature flag is disabled for the group' do
+        before do
+          stub_feature_flags(group_administration_nav_item: { enabled: false, thing: group })
+        end
+
+        it 'returns false' do
+          expect(helper.show_administration_nav?(group)).to be false
+        end
+      end
     end
   end