pihole-ftl: Download macvendor.db in setup service

As done in the update script https://github.com/pi-hole/pi-hole/blob/cef7fd4b02c9ae4314e7478c0d542379bfce7f65/automated install/basic-install.sh#L1791-L1792

nixos/modules/services/networking/pihole-ftl-setup-script.nix

···
       comment = list.description;
     };
   payloads = map makePayload cfg.lists;
+  macvendorURL = lib.strings.escapeShellArg cfg.macvendorURL;
 in
 ''
   # Can't use -u (unset) because api.sh uses API_URL before it is set
···
   pihole="${lib.getExe pihole}"
   jq="${lib.getExe pkgs.jq}"
 
+  ${lib.getExe pkgs.curl} --retry 3 --retry-delay 5 "${macvendorURL}" -o "${cfg.settings.files.macvendor}" || echo "Failed to download MAC database from ${macvendorURL}"
+
   # If the database doesn't exist, it needs to be created with gravity.sh
-  if [ ! -f '${cfg.stateDirectory}'/gravity.db ]; then
+  if [ ! -f '${cfg.settings.files.gravity}' ]; then
     $pihole -g
     # Send SIGRTMIN to FTL, which makes it reload the database, opening the newly created one
     ${lib.getExe' pkgs.procps "kill"} -s SIGRTMIN $(systemctl show --property MainPID --value ${config.systemd.services.pihole-ftl.name})

nixos/modules/services/networking/pihole-ftl.nix

···
       '';
     };
 
+    macvendorURL = mkOption {
+      type = types.str;
+      default = "https://ftl.pi-hole.net/macvendor.db";
+      description = ''
+        URL from which to download the macvendor.db file.
+      '';
+    };
+
     pihole = mkOption {
       type = types.package;
       default = piholeScript;