did:key with jwk_jcs-pub multicodec

[Voronar]

Hello!
What do you think about adding 'jwk_jcs-pub' multicodec handler as a feature flag for did-key crate?

More about the subject: w3c-ccg/did-method-key#63.

P.S. DID document resolving is not a problem, but one's creation is a bit trickier. We can define a new method under a feature flag on DIDKey struct named generate_jwk_jcs_pub to handle this specific case.

P.P.S. If anyone interested in the subject I can submit PR with an implementation.
main...Voronar:ssi:did_key_jwk_jcs_pub

[ianhamilton87]

FYI, I have a PR for the resolution of did:key with that codec.
The EBSI is specifying that DID method + multicodec to identify people.

I did avoid the creation as I saw creation being rather tricky since you couldn't just base the multicodec entirely off the type of key presented. @Voronar - i'd be interested in your implementation of creating such a key!