refactor: split configurations for fail2ban, postgres, and qbittorent into folders

modules/nixos-modules/server/postgres/impermanence.nix

@@ -0,0 +1,27 @@
+{
+  config,
+  lib,
+  ...
+}: let
+  dataDir = "/var/lib/postgresql/16";
+in {
+  config = lib.mkIf (config.host.postgres.enable && config.host.impermanence.enable) {
+    assertions = [
+      {
+        assertion = config.services.postgresql.dataDir == dataDir;
+        message = "postgres data directory does not match persistence";
+      }
+    ];
+    environment.persistence."/persist/system/root" = {
+      enable = true;
+      hideMounts = true;
+      directories = [
+        {
+          directory = dataDir;
+          user = "postgres";
+          group = "postgres";
+        }
+      ];
+    };
+  };
+}