Change machine name from @localhost to @<servername> in routes

[jcolebrand]

Background: I've recently upgraded to 318 from (Fedora 37 default install) and my nginx interrupted because the new pathing looks for an @localhost in the path, which is something I had as part of a tool to help deter bad actors via my nginx config. Previously it did not look for that in the URL, so something is new, but I don't know what.

Goal: https://<snip>/cockpit/@localhost/shell/shell.css should look like https://<snip>/cockpit/@<serverIdentifier>/shell/shell.css (as an example URL, and not the only URL I want to change)

Surely this is config driven, but the documentation does not help me as clearly as it might help someone else.

I could potentially add something to /etc/cockpit/cockpit.conf or to machines.d or ...? I'm just not sure what that thing is.

Motivation: I don't want urls through my nginx from my servers to allow refs to "localhost" (as those should be behind reverse proxies, and, it's a headless server, so why would I ever serve "traffic" to "localhost" from those machines "publicly")

If this is not possible because "referring to the primary host where Cockpit is installed has to be localhost, and here's the link to the line that forces it in the repo" then I will spend some time to help change that :D

Cheers and thanks folks.