Update flake

common/default.nix

@@ -5,6 +5,7 @@
     ./constants.nix
     ./secrets.nix
     ./users.nix
+    ./nix.nix
   ];
 
   home-manager.sharedModules = [inputs.plasma-manager.homeManagerModules.plasma-manager];

common/nix.nix

@@ -0,0 +1,22 @@
+{config, ...}: {
+  nix = {
+    gc = {
+      automatic = true;
+      options = "--delete-older-than 30d";
+    };
+    settings = {
+      auto-optimise-store = true;
+      experimental-features = ["nix-command" "flakes"];
+      trusted-users = [config.constants.userName];
+    };
+  };
+  nixpkgs = {
+    config.allowUnfree = true;
+    config.permittedInsecurePackages = [
+      "aspnetcore-runtime-6.0.36"
+      "aspnetcore-runtime-wrapped-6.0.36"
+      "dotnet-sdk-6.0.428"
+      "dotnet-sdk-wrapped-6.0.428"
+    ];
+  };
+}