Add authorisation check for ManagementController

app/controllers/management/management_controller.rb

@@ -1,5 +1,13 @@
 module Management
   class ManagementController < ::ApplicationController
+    before_action :authenticate_user!, :authorize_user!
+
     layout 'management'
+
+    private
+
+    def authorize_user!
+      head :forbidden unless current_user.admin?
+    end
   end
 end