Show only root namespaces for subscriptions

We only allow subscriptions for root namespaces. However, we also
rendered sub-groups when creating a subscription.
This was not an issue so far, because we only used the new
subscription sites for sign up, therefore users were not able to
create sub-groups beforehand.

This will change in the future, where we also want to use the
new subscription page design for upgrades.

ee/app/controllers/subscriptions_controller.rb

@@ -42,7 +42,7 @@ class SubscriptionsController < ApplicationController
     current_user.update(setup_for_company: true) if params[:setup_for_company]
 
     if params[:selected_group]
-      group = current_user.managed_free_namespaces.find(params[:selected_group])
+      group = current_user.manageable_groups_eligible_for_subscription.find(params[:selected_group])
     else
       group_name = params[:setup_for_company] ? customer_params[:company] : "#{current_user.name}'s Group"
       path = Namespace.clean_path(group_name)

ee/app/helpers/subscriptions_helper.rb

@@ -39,7 +39,7 @@ module SubscriptionsHelper
   end
 
   def group_data
-    current_user.managed_free_namespaces.with_counts(archived: false).map do |namespace|
+    current_user.manageable_groups_eligible_for_subscription.with_counts(archived: false).map do |namespace|
       {
         id: namespace.id,
         name: namespace.name,

ee/app/models/ee/user.rb

@@ -250,8 +250,9 @@ module EE
         .any?
     end
 
-    def managed_free_namespaces
+    def manageable_groups_eligible_for_subscription
       manageable_groups
+        .where(parent_id: nil)
         .left_joins(:gitlab_subscription)
         .merge(GitlabSubscription.left_joins(:hosted_plan).where(plans: { name: [nil, *::Plan.default_plans] }))
         .order(:name)

ee/changelogs/unreleased/nicolasdular-root-namespaces-for-paid-signup.yml

+---
+title: Show only root namespaces for subscriptions
+merge_request: 38481
+author:
+type: fixed

ee/spec/controllers/subscriptions_controller_spec.rb

@@ -205,6 +205,12 @@ RSpec.describe SubscriptionsController do
 
           expect(response.body).to eq({ location: "/#{selected_group.path}" }.to_json)
         end
+
+        context 'when selected group is a sub group' do
+          let(:selected_group) { create(:group, parent: create(:group))}
+
+          it { is_expected.to have_gitlab_http_status(:not_found) }
+        end
       end
 
       context 'when selecting a non existing group' do

ee/spec/models/user_spec.rb

@@ -996,13 +996,14 @@ RSpec.describe User do
     end
   end
 
-  describe '#managed_free_namespaces' do
+  describe '#manageable_groups_eligible_for_subscription' do
     let_it_be(:user) { create(:user) }
     let_it_be(:licensed_group) { create(:group, gitlab_subscription: create(:gitlab_subscription, :bronze)) }
     let_it_be(:free_group_z) { create(:group, name: 'AZ', gitlab_subscription: create(:gitlab_subscription, :free)) }
     let_it_be(:free_group_a) { create(:group, name: 'AA', gitlab_subscription: create(:gitlab_subscription, :free)) }
+    let_it_be(:sub_group) { create(:group, name: 'SubGroup', parent: free_group_a) }
 
-    subject { user.managed_free_namespaces }
+    subject { user.manageable_groups_eligible_for_subscription }
 
     context 'user with no groups' do
       it { is_expected.to eq [] }
@@ -1047,6 +1048,8 @@ RSpec.describe User do
       end
 
       it { is_expected.to eq [free_group_a, free_group_z] }
+
+      it { is_expected.not_to include(sub_group) }
     end
   end