Set Private visibility for restricted Internal imported projects

With https://gitlab.com/gitlab-org/gitlab-ee/issues/12388 change going
live there is potential risk of breaking imports of 'Internal' projects.
This change makes sure if 'Internal' visibility level is restricted
all 'Internal' projects will be marked as 'Private'

See: https://gitlab.com/gitlab-org/gitlab-ce/issues/64311

changelogs/unreleased/georgekoltsov-64311-set-visibility-private-if-internal-restricted.yml

+---
+title: Set visibility level 'Private' for restricted 'Internal' imported projects when 'Internal' visibility setting is restricted in admin settings
+merge_request: 30522
+author:
+type: other

doc/user/project/settings/import_export.md

@@ -116,3 +116,8 @@ For more details on the specific data persisted in a project export, see the
 
 1. Click on **Import project** to begin importing. Your newly imported project
    page will appear soon.
+
+NOTE: **Note:**
+If use of the `Internal` visibility level
+[is restricted](../../../public_access/public_access.md#restricting-the-use-of-public-or-internal-projects),
+all imported projects are given the visibility of `Private`.

lib/gitlab/import_export/project_tree_restorer.rb

@@ -130,6 +130,7 @@ module Gitlab
       def visibility_level
         level = override_params['visibility_level'] || json_params['visibility_level'] || @project.visibility_level
         level = @project.group.visibility_level if @project.group && level.to_i > @project.group.visibility_level
+        level = Gitlab::VisibilityLevel::PRIVATE if level == Gitlab::VisibilityLevel::INTERNAL && Gitlab::CurrentSettings.restricted_visibility_levels.include?(level)
 
         { 'visibility_level' => level }
       end

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -496,6 +496,18 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
       end
     end
 
+    context 'with restricted internal visibility' do
+      describe 'internal project' do
+        let(:visibility) { Gitlab::VisibilityLevel::INTERNAL }
+
+        it 'uses private visibility' do
+          stub_application_setting(restricted_visibility_levels: [Gitlab::VisibilityLevel::INTERNAL])
+
+          expect(restorer.restored_project.visibility_level).to eq(Gitlab::VisibilityLevel::PRIVATE)
+        end
+      end
+    end
+
     context 'with group visibility' do
       before do
         group = create(:group, visibility_level: group_visibility)
@@ -528,6 +540,14 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         it 'uses the group visibility' do
           expect(restorer.restored_project.visibility_level).to eq(group_visibility)
         end
+
+        context 'with restricted internal visibility' do
+          it 'sets private visibility' do
+            stub_application_setting(restricted_visibility_levels: [Gitlab::VisibilityLevel::INTERNAL])
+
+            expect(restorer.restored_project.visibility_level).to eq(Gitlab::VisibilityLevel::PRIVATE)
+          end
+        end
       end
     end
   end