nix: refactor modules pass 1

nix/configurations/installer.nix

@@ -0,0 +1,36 @@
+let
+  system = "x86_64-linux";
+  self = import ../../default.nix {};
+in
+  {
+    pkgs,
+    modulesPath,
+    ...
+  }: {
+    imports = [
+      {
+        nixpkgs = {
+          hostPlatform = system;
+          overlays = [self.overlays.default self.overlays.packages'];
+        };
+      }
+
+      ../nixosModules/common/system-nixconf.nix
+      ../nixosModules/extra/layouts
+
+      (modulesPath + "/installer/cd-dvd/installation-cd-minimal.nix")
+    ];
+    isoImage.squashfsCompression = "zstd -Xcompression-level 3";
+    environment.systemPackages = [
+      pkgs.disko
+      pkgs.fish
+      pkgs.git
+      pkgs.pastebinit # for sharing cli output & debugging
+      pkgs.hdparm # to ATA secure wipe disks
+      pkgs.btop
+      pkgs.just # run my helpers
+    ];
+    networking.firewall.allowedTCPPorts = [8080]; # in case you wanna nc
+    users.users.nixos.shell = pkgs.fish;
+    programs.fish.enable = true;
+  }