Following changes in https://github.com/NixOS/nixpkgs/pull/91092 the `path` attribute is now a list
instead of being a string. This resulted resulted in the following evaluation error:
"cannot coerce a list to a string, at [...]/nixos/modules/services/networking/openvpn.nix:16:18"
so we now need to convert it to the right type ourselves.
Closes https://github.com/NixOS/nixpkgs/issues/97360.
cb141359bf