feat: refactored configs to follow modules pattern

modules/hosts/nixos/installer/configuration.nix

@@ -0,0 +1,26 @@
+{...}: {
+  flake.nixosModules.installer-configuration = {
+    lib,
+    pkgs,
+    modulesPath,
+    ...
+  }: {
+    imports = [(modulesPath + "/installer/cd-dvd/installation-cd-minimal.nix")];
+
+    systemd.services.sshd.wantedBy = pkgs.lib.mkForce ["multi-user.target"];
+    users.users.root.openssh.authorizedKeys.keys = [
+      "ssh-ed25519 AaAeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee username@host"
+    ];
+
+    isoImage.squashfsCompression = "gzip -Xcompression-level 1";
+
+    networking.hostName = "installer";
+
+    nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+
+    host.users.leyla = {
+      isPrincipleUser = true;
+      isTerminalUser = true;
+    };
+  };
+}