Revert "nixosModules,pkgs: remove installer. clanModules: init installer module"

This reverts commit 29a7f0312b.

nixosModules/bcachefs.nix

@@ -0,0 +1,16 @@
+{
+  lib,
+  pkgs,
+  config,
+  ...
+}:
+{
+  # If we also need zfs, we can use the unstable version as we otherwise don't have a new enough kernel version
+  boot.zfs.package = pkgs.zfsUnstable;
+  boot.kernelPackages = lib.mkIf config.boot.zfs.enabled (
+    lib.mkForce config.boot.zfs.package.latestCompatibleLinuxPackages
+  );
+
+  # Enable bcachefs support
+  boot.supportedFilesystems.bcachefs = lib.mkDefault true;
+}