Support x5c element in JWK

[Justin Richer]

New example:

  {"keys":[
   {"kty":"RSA",
    "use":"sig",
    "kid":"1b94c",
    "n":"vrj…",
    "e":"AQAB",
    "x5c":
     ["MII…=="]}
  ]}

[Vladimir Dzhuvinov]

Hi Justin,

The "x5c" parameter isn't part of the official JWK spec (as of version -10), right? I only remember there being a discussion about it on the JOSE list, but didn't follow the details.

[Justin Richer]

That's correct, it's slated for the next version of JWK that we should see in a couple weeks. We don't support the PKIX keytype right now anyway so this will be more of an enhancement than a breaking change.

[Vladimir Dzhuvinov]

Done in commit f8163e2 :)

However, I don't like the huge JWK constructors we now ended up having, will think of a suitable builder pattern to make it easier to construct JWKs.