use system.autoUpgrade for nixos machines

also add garnix.io cache

Closes #18

modules/base/common.nix

@@ -20,10 +20,12 @@
     settings = {
       substituters = [
         "https://walkah.cachix.org"
+        "https://cache.garnix.io"
       ];
 
       trusted-public-keys = [
         "walkah.cachix.org-1:D8cO78JoJC6UPV1ZMgd1V5znpk3jNUERGIeAKN15hxo="
+        "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g="
       ];
     };
   };

modules/base/nixos.nix

@@ -1,4 +1,4 @@
-_: {
+{ config, ... }: {
 
   imports = [ ./common.nix ];
 
@@ -20,5 +20,13 @@ _: {
     mosh.enable = true;
   };
 
-  system.stateVersion = "23.05";
+  system = {
+    autoUpgrade = {
+      enable = true;
+      flake = "github:walkah/athens#${config.networking.hostName}";
+      dates = "daily";
+      randomizedDelaySec = "5m";
+    };
+    stateVersion = "23.05";
+  };
 }