support PATCH

[kirlen]

As we're seeing with Fresh Annotator, as session data size grows it's going to be increasingly impractical to support only wholesale updates to our sessions. We need to implement the ability to submit updates as diffs instead.

This is a non-trivial task. Facebook's GraphQL is an example of how this can be supported. We may even be able to leverage GraphQL directly.

[kirlen]

Matthew, as a background task, pls start looking into this :)

[kirlen]

(and asyrique and i will too...)

[asyrique]

@kirlen and me are looking into using the JSONPath spec as way to implement PATCH