Move nixosHostConfig out of flake.nix

lib/nixosHostConfig.nix

@@ -0,0 +1,40 @@
+{ inputs, nixpkgs, nixpkgs-unstable, compose2nix, disko, flox, genebean-omp-themes,
+    home-manager, nix-darwin, nix-flatpak, nix-homebrew, nixos-cosmic,
+    nixos-hardware, nixpkgs-terraform, simple-nixos-mailserver, sops-nix, ...
+}: {
+  nixosHostConfig = { system ? "x86_64-linux", hostname, username ? "gene", additionalModules ? [], additionalSpecialArgs ? {} }: nixpkgs.lib.nixosSystem {
+    inherit system;
+    specialArgs = { inherit inputs compose2nix hostname username; } // additionalSpecialArgs;
+    modules = [
+      # move this to a common file later
+      ({
+        nixpkgs = {
+          config = {
+            allowUnfree = true;
+            permittedInsecurePackages = [ "olm-3.2.16" "electron-27.3.11" ];
+          };
+          overlays = [ nixpkgs-terraform.overlays.default ];
+        };
+      })
+
+      disko.nixosModules.disko
+
+      home-manager.nixosModules.home-manager {
+        home-manager = {
+          extraSpecialArgs = { inherit genebean-omp-themes hostname username; };
+          useGlobalPkgs = true;
+          useUserPackages = true;
+          users.${username}.imports = [
+            ../modules/home-manager/hosts/${hostname}/${username}.nix
+          ];
+        };
+      }
+
+      nix-flatpak.nixosModules.nix-flatpak
+
+      sops-nix.nixosModules.sops # system wide secrets management
+      ../modules/system/common/all-nixos.nix # system-wide stuff
+      ../modules/hosts/nixos/${hostname} # host specific stuff
+    ] ++ additionalModules;
+  };
+}