nixos/paperless: Support remote databases

When the database is on another host, unit isolation for the document
consumer and scheduler have to be disabled. This is currently enabled by
default via `PrivateNetwork = false` in defaultServiceConfig. Following
https://github.com/NixOS/nixpkgs/pull/368137#pullrequestreview-2522617890
making this conditional on the `database.createLocally` option.

nixos/modules/services/misc/paperless.nix

@@ -331,6 +331,7 @@ in
         ExecStart = "${cfg.package}/bin/celery --app paperless beat --loglevel INFO";
         Restart = "on-failure";
         LoadCredential = lib.optionalString (cfg.passwordFile != null) "PAPERLESS_ADMIN_PASSWORD:${cfg.passwordFile}";
+        PrivateNetwork = cfg.database.createLocally; # defaultServiceConfig enables this by default, needs to be disabled for remote DBs
       };
       environment = env;
 
@@ -407,6 +408,7 @@ in
         User = cfg.user;
         ExecStart = "${cfg.package}/bin/paperless-ngx document_consumer";
         Restart = "on-failure";
+        PrivateNetwork = cfg.database.createLocally; # defaultServiceConfig enables this by default, needs to be disabled for remote DBs
       };
       environment = env;
       # Allow the consumer to access the private /tmp directory of the server.