Mounting engine in namespace

I am testing an engine which normally is mounted at /

NotifyMe::Application.routes.draw do

mount_opro_oauth :controllers => {:oauth_client_apps =>


I am trying to mount it inside my existing backoffice namespace, is it
possible or not advisable

namespace :backoffice do
 match '/', to: 'dashboards#show'
  resource :dashboards, :only => :show

mounting it at root give me urls like :


but as it’s a backoffice process, I would like to have urls like:


I tried to move the mount line inside the namespace, but then I got
with the engine routes…
I thought /backoffice would have been added automatically

thanks for your feedback