feat(django-apps): make backups optional

modules/nixos/django-apps/default.nix

@@ -441,6 +441,10 @@ in
                   This is relative to the base directory, e.g. the parent of the source directory.
                 '';
               };
+
+              doBackups = mkEnableOption "backups for this site" // {
+                default = true;
+              };
             };
           }
         )
@@ -856,7 +860,9 @@ in
       #   name: _: nameValuePair "dj-${name}" { settings.paths = [ "/var/lib/private/django-apps/${name}" ]; }
       # ) cfg.sites;
       postgresDatabases = builtins.map (name: "dj-${name}") (
-        attrNames (filterAttrs (_: { dbType, ... }: dbType == "postgresql") cfg.sites)
+        attrNames (
+          filterAttrs (_: { dbType, doBackups, ... }: doBackups && dbType == "postgresql") cfg.sites
+        )
       );
     };
   };