Create POJOs to support JSON API spec Responses

[dneufeldcu]

Summary

As a	a developer supporting multiple future search responses
I want to be able to	generate output formats more easily and with less bugs.
So that I can	in the future it is easier to update the response formats and support new formats

JSON API Spec reference

Tasks

• [ ] Consolidate ES responses into one location
• [ ] Create the POJOs to support response model
• [ ] Update to POJOs away from Groovy maps hard coded responses (OS Search)
• [ ] Need to ensure responses are meeting JSON API schema

[mcquinne]

Probably worth taking a look at the server-side libraries mentioned on the JSON API site: https://jsonapi.org/implementations/#server-libraries-java

We should be careful not to pull in something with too much of a learning curve, but on the other hand it could be a good opportunity to avoid reinventing something.