Reject creating boards when the feature is not available

app/controllers/ee/projects/boards_controller.rb

@@ -3,6 +3,7 @@ module EE
     module BoardsController
       extend ActiveSupport::Concern
       prepended do
+        before_action :check_multiple_issue_boards_available!, only: [:create]
         before_action :authorize_admin_board!, only: [:create, :update, :destroy]
         before_action :find_board, only: [:update, :destroy]
       end

spec/controllers/ee/projects/boards_controller_spec.rb

@@ -30,6 +30,11 @@ describe Projects::BoardsController do # rubocop:disable RSpec/FilePath
   end
 
   describe 'POST create' do
+    context 'with the multiple issue boards available' do
+      before do
+        stub_licensed_features(multiple_issue_boards: true)
+      end
+
       context 'with valid params' do
         it 'returns a successful 200 response' do
           create_board name: 'Backend'
@@ -65,6 +70,15 @@ describe Projects::BoardsController do # rubocop:disable RSpec/FilePath
           expect(response).to have_http_status(404)
         end
       end
+    end
+
+    it 'renders a 404 when multiple issue boards are not available' do
+      stub_licensed_features(multiple_issue_boards: false)
+
+      create_board name: 'Backend'
+
+      expect(response).to have_http_status(404)
+    end
 
     def create_board(name:)
       post :create, namespace_id: project.namespace.to_param,