[candlepin] Serializing model.KeyPair to JSON

[jesus rodriguez]

So I've hit a little snag trying to get model.KeyPair to serialize to 
JSON (because this will make importing easier).

I keep getting the error as seen here: https://gist.github.com/4081176

The problem is that it's trying to JSONify the PrivateKey and PublicKey 
which makes sense from a default ObjectMapper. What I'd really like is 
that it treat those as PEMEncoded bytes like we do when we serialize the 
IdentityCertificate or EntitlementCertificate.

Now I was thinking this would require a custom serializer, but that 
seemed heavy handed and smelled (my nose so stuffed I really didn't 
smell anything) of overengineering because we haven't needed a custom 
one so far.

Any thoughts on how best to serialize this to the manifest? Is the 
custom serializer the best way? Or maybe add methods that return byte[] 
and have jackson ignore the Private and Public key methods?

Thoughts?

jesus