The Backstage backend restricts what resources can be fetched by default. This guide describes how to configure this list. This would allow you to do something like fetch a public API definition in a catalog info file.
By default only *.example.com and *.mozilla.org are allowed.
administration/settings/backend in Roadie you should be able to click “add item” then enter the hostname of
the resource you want to access in the host field and click “Save” then “Apply & restart”.
If you want to restrict access further you can add a list of paths and only resources under those paths will be allowed.