Add a generic backup solution.

nixos/common/backups.nix

@@ -0,0 +1,11 @@
+{lib, ...}: let
+  inherit (lib) mkOption types;
+in {
+  # Generic Backups.
+  options.foehammer.backups = {
+    paths = mkOption {
+      type = types.nullOr (types.listOf types.str);
+      default = [];
+    };
+  };
+}

nixos/common/services/vaultwarden.nix

@@ -43,6 +43,10 @@ in {
       SIGNUPS_ALLOWED = cfg.signups;
     };
 
+    foehammer.backups.paths = [
+      "/var/lib/bitwarden_rs"
+    ];
+
     environmentFile = cfg.envPath;
   };
 }