nix: use home-manager to generate nixConf

nix/configurations/combinators.nix

@@ -10,6 +10,8 @@ let
     nix.registry.nixpkgs.flake = inputs.nixpkgs;
   };
 
+  substituters = import ./substituters.nix;
+
   mkNixOS =
     name: sys: hmOpts:
     withSystem sys (
@@ -27,6 +29,7 @@ let
           "${self}/nix/hosts/${name}"
           "${self}/nix/layouts"
           inputs.agenix.nixosModules.default
+          substituters
           inputs.home-manager.nixosModules.home-manager
           {
             home-manager = {
@@ -38,6 +41,7 @@ let
                 "${self}/nix/home/${name}"
                 nixpkgsRegistry
                 hmOpts
+                substituters
               ];
             };
           }
@@ -62,6 +66,7 @@ let
           "${self}/nix/hosts/_"
           "${self}/nix/hosts/_darwin"
           "${self}/nix/hosts/${name}"
+          substituters
           inputs.home-manager.darwinModules.home-manager
           {
             home-manager = {
@@ -72,6 +77,7 @@ let
                 "${self}/nix/home/_"
                 "${self}/nix/home/${name}"
                 nixpkgsRegistry
+                substituters
                 hmOpts
               ];
             };
@@ -97,6 +103,7 @@ let
           "${self}/nix/home/_"
           "${self}/nix/home/${name}"
           nixpkgsRegistry
+          substituters
           hmOpts
         ];
       }

nix/configurations/substituters.nix

@@ -0,0 +1,27 @@
+{ pkgs, ... }:
+{
+  nix.package = pkgs.nixVersions.nix_2_21;
+  nix.settings = {
+    /*
+      substituters can only be used by users that are trusted by nix -> nix trusts the user to do it right
+      trusted-substituters can be used by any user -> nix trusts everything the substituter provides
+
+      "In addition, each store path should be trusted as described in trusted-public-keys"
+      -> keys for everything
+    */
+
+    substituters = [
+      "https://nix-community.cachix.org"
+      "https://leana8959.cachix.org"
+    ];
+
+    trusted-substituters = [
+      "https://leana8959.cachix.org"
+      "https://nix-community.cachix.org"
+    ];
+    trusted-public-keys = [
+      "leana8959.cachix.org-1:CxQSAp8lcgMv8Me459of0jdXRW2tcyeYRKTiiUq8z0M="
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+    ];
+  };
+}