gistfile1.txt

      desc 'add achievement to user'
      params do
        requires :id, type: String, desc: "Status ID."
        requires :achievement_id, type: String, desc: "Achievement id you want to add"
      end
      put ':id' do
        user = User.find params[:id]
        achievement = Achievement.find params[:achievement_id]
        user.achievements << achievement
      end