Show service templates nav based on FF

Put Service Templates nav item behind a featureflag,
currently disabled by default. When enabled,
the link won't be present in the UI.

app/helpers/services_helper.rb

@@ -172,6 +172,14 @@ module ServicesHelper
       name: integration.to_param
     }
   end
+
+  def service_templates_enabled?
+    Feature.disabled?(:disable_service_templates, type: :development, default_enabled: :yaml)
+  end
+
+  def show_service_templates_nav_link?
+    service_templates_enabled?
+  end
 end
 
 ServicesHelper.prepend_if_ee('EE::ServicesHelper')

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

@@ -202,6 +202,7 @@
 
       = render_if_exists 'layouts/nav/sidebar/credentials_link'
 
+      - if show_service_templates_nav_link?
         = nav_link(controller: :services) do
           = link_to admin_application_settings_services_path do
             .nav-icon-container

config/feature_flags/development/disable_service_templates.yml

+---
+name: disable_service_templates
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/59098
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/327436
+milestone: '13.12'
+type: development
+group: group::ecosystem
+default_enabled: false

spec/features/admin/admin_settings_spec.rb

@@ -251,8 +251,20 @@ RSpec.describe 'Admin updates settings' do
       end
     end
 
+    context 'when Service Templates are enabled' do
+      before do
+        stub_feature_flags(disable_service_templates: false)
+      end
+
+      context 'when no service templates are active' do
+        it 'does not show Service Templates link' do
+          expect(page).not_to have_link('Service Templates')
+        end
+      end
+
       context 'when the Slack Notifications Service template is active' do
         before do
+          stub_feature_flags(disable_service_templates: false)
           create(:service, :template, type: 'SlackService', active: true)
 
           visit general_admin_application_settings_path
@@ -288,6 +300,17 @@ RSpec.describe 'Admin updates settings' do
           expect(find_field('Deployment')).not_to be_checked
         end
       end
+    end
+
+    context 'When Service templates are disabled' do
+      before do
+        stub_feature_flags(disable_service_templates: true)
+      end
+
+      it 'does not show Service Templates link' do
+        expect(page).not_to have_link('Service Templates')
+      end
+    end
 
     context 'Integration page', :js do
       before do