Don't show integrations overrides tab at group lvl

Instance and group-level integrations pages share
the same haml templates, and there was a bu
where the instance-level overrides navigation tab
was displayed at the group-level.

This commit fixes that and adds a test.

app/helpers/integrations_helper.rb

@@ -128,7 +128,9 @@ module IntegrationsHelper
   def integration_tabs(integration:)
     [
       { key: 'edit', text: _('Settings'), href: scoped_edit_integration_path(integration) },
-      ({ key: 'overrides', text: s_('Integrations|Projects using custom settings'), href: scoped_overrides_integration_path(integration) } if instance_level_integration_overrides?)
+      (
+        { key: 'overrides', text: s_('Integrations|Projects using custom settings'), href: scoped_overrides_integration_path(integration) } if integration.instance_level? && instance_level_integration_overrides?
+      )
     ].compact
   end
 

spec/features/groups/integrations/user_activates_mattermost_slash_command_spec.rb

@@ -13,4 +13,9 @@ RSpec.describe 'User activates the group-level Mattermost Slash Command integrat
   let(:edit_path) { edit_group_settings_integration_path(group, :mattermost_slash_commands) }
 
   include_examples 'user activates the Mattermost Slash Command integration'
+
+  it 'does not display the overrides tab' do
+    expect(page).not_to have_link('Settings', href: edit_path)
+    expect(page).not_to have_link('Projects using custom settings', href: overrides_admin_application_settings_integration_path(:mattermost_slash_commands))
+  end
 end