`hps::to_string()` method fails to serialize a struct with `enum class` member as it complain no `serialize` method found inside enum class. Is there a way to serialize/deserialize structs with enum fields ? Source tag: [8d14036](https://github.com/jl2922/hps/commit/8d1403697a2fad6ddf02c7afb190596ca68b2105)