Integrating separate apps into one Rails App

I have built multiple Rails Applications that handle the various
services I run, e.g. Mail, DNS, Radius etc.

I want to bring all those apps together under one umbrella to have a
centralised login system so that I can start working on user
permissions, i.e. each user can login and view/change the information
that relates to him as well as look at graphs and such.

My end goal is if we deploy a service, to build the service separately,
and then drop it into the main system, adding menu items as need be.

Is the best way to do this using components or plugins?