json references

[Emmanouil Batsis (Manos)]

It looks like I will be implementing json references in my resthub app
using Jackson's @JsonIdentityInfo on the spring stack and a simple
identity/model map on the backbone stack as mentioned in [1] as reducing
request/response bodies has become an issue for some time.

I would be interested in making this reusable via a patch that allows
for this as an optional feature or, if that does not prove very
practical, a suitable howto for the resthub documentation.

One issue is identity scope. My understanding is JsonIdentityInfo
naturally only applies as a ref under the scope of a single request as
it cannot be aware if the client actually desires a fresh serialization
of the object or even if it has already loaded it in the same "session"
whatever the meaning of that may be. I was thus wondering if it may be a
good idea to restrict the scope of the client side map to a single
request; this may provide a drop-in optimization as a feature with
virtually no side effects.

[1]
https://github.com/resthub/resthub-backbone-stack/issues/87#issuecomment-12688743

Manos