feat: refactor the modules/servers directory.

modules/servers/per-server/bragi/default.nix

@@ -0,0 +1,15 @@
+{...}: let
+  servicesDir = ./services;
+  serviceFiles =
+    builtins.filter
+    (name: builtins.match "^.*\\.nix$" name != null)
+    (builtins.attrNames (builtins.readDir servicesDir));
+  hostModules = map (fn: import "${servicesDir}/${fn}") serviceFiles;
+in {
+  imports =
+    [
+      ../../common
+      ./secrets.nix
+    ]
+    ++ hostModules;
+}