Add support for garde crate as alternative to validator

[jirutka]

Can you please consider adding support for garde as an alternative to validator? It’s better designed than validator. The reasons for starting a new project are mentioned in https://github.com/Keats/validator/issues/201.

[Wicpar]

+1 this request, validator does not support enums. In the mean time validator can be replaced, structs will just have duplicate attrs with #[garde] and #[validate]