Rust enum support

[angelorodem]

Hi, i could not find the reason on gh issues or in other places,
what is the current limitation that prevents an implementation that is able to Serialize/Deserialize rust non C-like enums?
is that some limitation because it is not possible in no_std or is just a missing feature?

[ryan-summers]

I had one question when reading this: How does a complex rust enum map into json object representations?

• Seems like this is possible without alloc, so we could likely follow what serde-json does (see https://github.com/serde-rs/json/blob/master/tests/test.rs#L496)

After researching serde-json, it seems to me like this is simply missing implementation. If you'd like to take it on, I'd be happy to review the change!