System/Servenix+Thinknix: Fix sops key issue, they key location assumed an impermanent setup

Changed the default location to /home/${username}/.secrets/age/age.key,
impermanent systems have to override this.

system/default.nix

@@ -91,8 +91,6 @@ with mylib.networking; {
 
     polkit.enable = true;
 
-    # TODO: This does not work on ServeNix?
-    #       Check on ThinkNix...
     sops-nix.bootSecrets.${username} = [
       "user-password"
     ];

system/modules/sops-nix/default.nix

@@ -26,9 +26,7 @@ in {
       defaultSopsFile = ./secrets.yaml;
 
       age = {
-        # NOTE: Sops needs the keys before impermanence kicks in
-        #       so we have to link to /persist directly...
-        keyFile = "/persist/home/${username}/.secrets/age/age.key";
+        keyFile = lib.mkDefault "/home/${username}/.secrets/age/age.key";
         generateKey = false;
         sshKeyPaths = [];
       };

system/nixinator/default.nix

@@ -85,6 +85,10 @@
     ];
   };
 
+  # NOTE: Sops needs the keys before impermanence kicks in
+  #       so we have to link to /persist directly...
+  sops.age.keyFile = "/persist/home/${username}/.secrets/age/age.key";
+
   sops.templates."makemkv-settings.conf" = {
     owner = config.users.users.${username}.name;
     content = ''