nixos/clan: add option for opting out of Clan defaults

Also replace `documentation.nixos.enable = false` with
`documentation.doc.enable` to opt out of only `nixos-help` and the HTML
manual but leave `man configuration.nix`.

nixosModules/clanCore/default.nix

@@ -1,10 +1,9 @@
-{ lib, config, ... }:
 {
   imports = [
     ./backups.nix
+    ./defaults.nix
     ./facts
     ./inventory
-    ./manual.nix
     ./meta/interface.nix
     ./metadata.nix
     ./networking.nix
@@ -12,7 +11,6 @@
     ./nix-settings.nix
     ./options.nix
     ./outputs.nix
-    ./packages.nix
     ./schema.nix
     ./sops.nix
     ./vars
@@ -22,14 +20,4 @@
     ./zfs.nix
   ];
 
-  # Use systemd during boot as well except:
-  # - systems with raids as this currently require manual configuration: https://github.com/NixOS/nixpkgs/issues/210210
-  # - for containers we currently rely on the `stage-2` init script that sets up our /etc
-  boot.initrd.systemd.enable = lib.mkDefault (!config.boot.swraid.enable && !config.boot.isContainer);
-
-  # Work around for https://github.com/NixOS/nixpkgs/issues/124215
-  documentation.info.enable = lib.mkDefault false;
-
-  # Don't install the /lib/ld-linux.so.2 stub. This saves one instance of nixpkgs.
-  environment.ldso32 = null;
 }