def show
      notification = Notification.find_by(id: params[:id])
      activity     = notification.activity

      notification.mark_as_read if notification.unread?

      redirect_to activity_activities_path(activity_id: activity.id)
    end
def show
      notification = Notification.find_by(id: params[:id])
      activity     = notification.activity

      notification.mark_as_read if notification.unread?

      redirect_to activity_activities_path(activity_id: activity.id)
    end
GET /notifications/1