update agenix shell pinning as a workaround for agenix las version not being properly push to nixpkgs

shared/mail/maddy.nix

@@ -0,0 +1,21 @@
+{ config, lib, pkgs, ... }:
+
+let
+    # Import nodes
+    nodes = import ./../../nodes.nix;
+    myName = config.hostName;
+    myNode = nodes."${myName}";
+
+    # And mapping
+    mapping = import ./../../mapping.nix;
+
+in
+{
+    age.secrets = {
+        "tsig" = {
+            file = ./../../secrets/mail/tsig.age;
+            owner = "knot";
+            group = "knot";
+        };
+    };
+}