hello
```networking.wireguard.interfaces.wg0 = {
  postSetup = "${pkgs.iproute}/bin/ip route add <vpn-public-ip> via <default-gateway>";
  postShutdown = "${pkgs.iproute}/bin/ip route del <vpn-public-ip> via <default-gateway>";
};
```
how would you specify default-gateway to be taken from DHCP?