Hide public groups from NotificationSettings view

In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/40326 we added
pagination for NotificationSettings view but accidentally removed
`all_available: false` from the service call, which makes all public
groups show up in the view and makes it much harder for a user to find
the group they're interested in.

app/controllers/profiles/notifications_controller.rb

@@ -35,6 +35,6 @@ class Profiles::NotificationsController < Profiles::ApplicationController
   private
 
   def user_groups
-    GroupsFinder.new(current_user).execute.order_name_asc.page(params[:page]).per(NOTIFICATIONS_PER_PAGE)
+    GroupsFinder.new(current_user, all_available: false).execute.order_name_asc.page(params[:page]).per(NOTIFICATIONS_PER_PAGE)
   end
 end

changelogs/unreleased/do_not_show_all_groups_on_notif_settings.yml

+---
+title: Do not show all public groups in global notification settings page
+merge_request: 40879
+author:
+type: fixed

spec/controllers/profiles/notifications_controller_spec.rb

@@ -54,19 +54,36 @@ RSpec.describe Profiles::NotificationsController do
     end
 
     context 'with group notifications' do
+      let(:notifications_per_page) { 5 }
+
       let_it_be(:group) { create(:group) }
       let_it_be(:subgroups) { create_list(:group, 10, parent: group) }
 
       before do
         group.add_developer(user)
         sign_in(user)
-        stub_const('Profiles::NotificationsController::NOTIFICATIONS_PER_PAGE', 5)
-        get :show
+        stub_const('Profiles::NotificationsController::NOTIFICATIONS_PER_PAGE', notifications_per_page)
       end
 
       it 'paginates the groups' do
+        get :show
+
         expect(assigns(:group_notifications).count).to eq(5)
       end
+
+      context 'when the user is not a member' do
+        let(:notifications_per_page) { 20 }
+
+        let_it_be(:public_group) { create(:group, :public) }
+
+        it 'does not show public groups', :aggregate_failures do
+          get :show
+
+          # Let's make sure we're grabbing all groups in one page, just in case
+          expect(assigns(:user_groups).count).to eq(11)
+          expect(assigns(:user_groups)).not_to include(public_group)
+        end
+      end
     end
 
     context 'with project notifications' do