[REQUEST] Ability to have OnionServices to reference svc's in another namespace

[samip5]

Is your feature request related to a problem? Please describe.
I don't want to deploy my app and Tor related things to the same ns as the OnionService.

Describe the solution you'd like
Ability to clearly state the allowed namespaces the Tor controller has access to.

Additional context
Currently it seems that the namespace the OnionService is deployed to determines where it will search for the specified service. This should be extended to support namespace syntax in name like svc.namespace