Custom transformer/converter

[sideeffffect]

Would it be possible to provide a custom transformer/converter that would be used for nested field?

Our usecase is that ScalaPB prduces case classes with ByteString fields, but in our domain case classes we use ByteVector (from scodec). So we would like to be able to provide a ByteString => ByteVector trasformer which would enable converting from ScalaPB to domain.

It would be analogous to Chimney's Transformer