Custom serializers

[johanhelsing]

It would be nice it was possible to customize what kind of serializer is used.

Currently it's hard-coded to rmp-serde (messagepack with struct maps) on native and serde_json on wasm.

[gilescope]

+1 - in my case I'd be happy storing and retrieving &[u8]

[davids91]

I'm all for that as well!