Replace policy check with license check and minor refactor

* Use license check
License.feature_available?(:adjourned_deletion_for_projects_and_groups)
instead of policy check can?(current_user, :delay_project_deletions)
* Remove `index_projects_on_hidden` as it was not used
* Update documentation

db/migrate/20220203134942_add_hidden_to_projects.rb

@@ -2,17 +2,10 @@
 
 class AddHiddenToProjects < Gitlab::Database::Migration[1.0]
   DOWNTIME = false
-  INDEX_NAME = 'index_projects_on_hidden'
 
-  disable_ddl_transaction!
+  enable_lock_retries!
 
-  def up
+  def change
     add_column :projects, :hidden, :boolean, default: false # rubocop: disable Migration/AddColumnsToWideTables
-    add_concurrent_index :projects, :hidden, name: INDEX_NAME
-  end
-
-  def down
-    remove_concurrent_index_by_name :projects, INDEX_NAME
-    remove_column :projects, :hidden
   end
 end

db/structure.sql

@@ -27547,8 +27547,6 @@ CREATE INDEX index_projects_on_creator_id_import_type_and_created_at_partial ON
 
 CREATE INDEX index_projects_on_description_trigram ON projects USING gin (description gin_trgm_ops);
 
-CREATE INDEX index_projects_on_hidden ON projects USING btree (hidden);
-
 CREATE INDEX index_projects_on_id_and_archived_and_pending_delete ON projects USING btree (id) WHERE ((archived = false) AND (pending_delete = false));
 
 CREATE UNIQUE INDEX index_projects_on_id_partial_for_visibility ON projects USING btree (id) WHERE (visibility_level = ANY (ARRAY[10, 20]));

doc/user/gitlab_com/index.md

@@ -88,7 +88,7 @@ Projects are permanently deleted after a seven-day delay.
 If you are on:
 
 - Premium tier and above, you can disable this by changing the [group setting](../group/index.md#enable-delayed-project-deletion).
-- Free tier, groups have delayed project deletion enabled by default and you cannot disable this setting.
+- Free tier, you cannot disable this setting or restore projects.
 
 ## Alternative SSH port
 

ee/app/controllers/ee/projects_controller.rb

@@ -38,7 +38,7 @@ module EE
 
     override :destroy
     def destroy
-      return super unless can?(current_user, :delay_project_deletions)
+      return super unless License.feature_available?(:adjourned_deletion_for_projects_and_groups)
       return super unless project.adjourned_deletion_configured?
       return super if project.marked_for_deletion_at? && params[:permanently_delete].present?
 

ee/app/policies/ee/global_policy.rb

@@ -14,11 +14,8 @@ module EE
       end
 
       condition(:adjourned_project_deletion_available) do
-        License.feature_available?(:adjourned_deletion_for_projects_and_groups)
-      end
-
-      condition(:project_owners_list_project_pending_deletion) do
-        (::Feature.enabled?(:project_owners_list_project_pending_deletion, default_enabled: :yaml) || can?(:admin_all_resources))
+        License.feature_available?(:adjourned_deletion_for_projects_and_groups) &&
+          (::Feature.enabled?(:project_owners_list_project_pending_deletion, default_enabled: :yaml) || can?(:admin_all_resources))
       end
 
       condition(:export_user_permissions_available) do
@@ -61,12 +58,8 @@ module EE
         prevent :create_group_with_default_branch_protection
       end
 
-      rule { adjourned_project_deletion_available & project_owners_list_project_pending_deletion }.policy do
-        enable :list_removable_projects
-      end
-
       rule { adjourned_project_deletion_available }.policy do
-        enable :delay_project_deletions
+        enable :list_removable_projects
       end
 
       rule { export_user_permissions_available & admin }.enable :export_user_permissions

ee/app/services/projects/mark_for_deletion_service.rb

@@ -4,7 +4,7 @@ module Projects
   class MarkForDeletionService < BaseService
     def execute
       return success if project.marked_for_deletion_at?
-      return error('Cannot mark project for deletion: feature not supported') unless can?(current_user, :delay_project_deletions)
+      return error('Cannot mark project for deletion: feature not supported') unless License.feature_available?(:adjourned_deletion_for_projects_and_groups)
 
       result = ::Projects::UpdateService.new(
         project,

ee/app/views/projects/_remove.html.haml

 - return unless can?(current_user, :remove_project, project)
-- can_delay_project_deletions = can?(current_user, :delay_project_deletions)
+- can_delay_project_deletions = License.feature_available?(:adjourned_deletion_for_projects_and_groups)
 - adjourned_deletion = project.adjourned_deletion_configured?
 - adjourned_date = adjourned_deletion ? permanent_deletion_date(Time.now.utc).to_s : nil
 - restore_help_path = help_page_path('user/project/settings/index', anchor: 'restore-a-project')

ee/app/views/projects/settings/_marked_for_removal.html.haml

-- return unless can?(current_user, :delay_project_deletions)
+- return unless License.feature_available?(:adjourned_deletion_for_projects_and_groups)
 
 %p= marked_for_removal_message(@project)

ee/lib/ee/api/projects.rb

@@ -125,7 +125,7 @@ module EE
 
           override :delete_project
           def delete_project(user_project)
-            return super unless can?(current_user, :delay_project_deletions)
+            return super unless License.feature_available?(:adjourned_deletion_for_projects_and_groups)
             return super unless user_project.adjourned_deletion_configured?
 
             result = destroy_conditionally!(user_project) do

ee/spec/policies/global_policy_spec.rb

@@ -293,24 +293,6 @@ RSpec.describe GlobalPolicy do
     end
   end
 
-  describe 'delay_project_deletions' do
-    before do
-      stub_licensed_features(adjourned_deletion_for_projects_and_groups: licensed?)
-    end
-
-    context 'when licensed feature is enabled' do
-      let(:licensed?) { true }
-
-      it { is_expected.to be_allowed(:delay_project_deletions) }
-    end
-
-    context 'when licensed feature is not enabled' do
-      let(:licensed?) { false }
-
-      it { is_expected.to be_disallowed(:delay_project_deletions) }
-    end
-  end
-
   describe ':export_user_permissions', :enable_admin_mode do
     using RSpec::Parameterized::TableSyntax