chore(test/makeTestClan): document all options, remove magic specialArgs

lib/test/sops.nix

@@ -0,0 +1,16 @@
+# nixosModule
+{ config, lib, ... }:
+{
+  # configures a static age-key to skip the age-key generation
+  sops.age.keyFile = "/run/age-key.txt";
+  system.activationScripts =
+    {
+      setupSecrets.deps = [ "age-key" ];
+      age-key.text = ''
+        echo AGE-SECRET-KEY-1PL0M9CWRCG3PZ9DXRTTLMCVD57U6JDFE8K7DNVQ35F4JENZ6G3MQ0RQLRV > /run/age-key.txt
+      '';
+    }
+    // lib.optionalAttrs (lib.filterAttrs (_: v: v.neededForUsers) config.sops.secrets != { }) {
+      setupSecretsForUsers.deps = [ "age-key" ];
+    };
+}