extend userSecret implementation to all users (not only root)

requires a patch of nixpkgs:

```diff
--- a/nixos/modules/contracts/default.nix       2025-09-07 16:15:41.381243855 +0200
+++ b/nixos/modules/contracts/default.nix       2025-09-08 00:05:58.218489096 +0200
@@ -87,7 +87,8 @@ in
               default = submodule (consumer: {
                 options = {
                   provider = mkOption {
-                    type = interface.config.provider;
+                    type = lib.types.nullOr interface.config.provider;
+                    default = null;
                   };
                   input = mkOption {
                     type = submodule interface.config.input;`

0 files changed, 0 insertions, 0 deletions