This will match the behavior in the upstream service which allows the user to set options to something that uses shell syntax.
persistent
Mirrors the `nix.gc.persistent` option in nixpkgs: https://search.nixos.org/options?channel=unstable&show=nix.gc.persistent&from=0&size=50&sort=relevance&type=packages&query=nix.gc.persistent
The nix-gc service runs automatically at a specified frequency. It is managed via launchd on macOS and systemd on Linux.