consolidate net-related stuff into hosts/common/net/ directory

hosts/common/default.nix

@@ -5,18 +5,16 @@
     ./fs.nix
     ./hardware
     ./home
-    ./hostnames.nix
     ./hosts.nix
     ./ids.nix
     ./machine-id.nix
-    ./net.nix
+    ./net
     ./nix-path
     ./persist.nix
     ./programs
     ./secrets.nix
     ./ssh.nix
     ./users
-    ./vpn.nix
   ];
 
   sane.nixcache.enable-trusted-keys = true;

hosts/common/net/default.nix

@@ -1,6 +1,10 @@
 { lib, pkgs, ... }:
 
 {
+  imports = [
+    ./hostnames.nix
+    ./vpn.nix
+  ];
   # the default backend is "wpa_supplicant".
   # wpa_supplicant reliably picks weak APs to connect to.
   # see: <https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/474>

hosts/common/net/hostnames.nix

@@ -1,4 +1,3 @@
-# TODO: move to hosts/common/
 { config, lib, ... }:
 
 {