refactor to conform to json-api document standard

[elrayle]

Description

It was suggested that QA be refactored to conform to the json-api document standard.

Rationale

Samvera community is committed to using industry standards when available.

Before and After changes

The json-api format would change the current format used for QA.

Search Results

BEFORE

[ { id: 1, label: "example title" } ]

AFTER

{
  data: [ { id: 1, label: "example title" } ]
}

For linked data module with optional performance data and header response

BEFORE

{ 
  performance_data: { ... }
  response_header: {
    start_record: 31          # the number of the first record returned
    requested_records: 10     # the number of records requested (aka page size)
    retrieved_records: 10     # the actual number of records returned in this request
    total_records: 85         # the total number of matches for this search request
  }
  results: [ { uri: "http://example.com/1", id: 1, label: "example title" } ]
}

AFTER

{ 
  meta: { performance_data: { ... } }
  links: { 
    pagination: {
      first: https://example.app.com/qa/search/linked_data/agrovoc_ld4l_cache?q=milk&page[offset]=21&page[limit]=10
      last: https://example.app.com/qa/search/linked_data/agrovoc_ld4l_cache?q=milk&page[offset]=81&page[limit]=10
      prev: https://example.app.com/qa/search/linked_data/agrovoc_ld4l_cache?q=milk&page[offset]=11&page[limit]=10
      next: https://example.app.com/qa/search/linked_data/agrovoc_ld4l_cache?q=milk&page[offset]=31&page[limit]=10
    }
  }
  data: [ { uri: "http://example.com/1", id: 1, label: "example title" } ]
}

Missing from this is the total count of records. More exploration is required to determine the best location to include this information.

Fetch/Show results

BEFORE

# results for a single term -- format varies by authority

AFTER

{
  data: # results for a single term -- format varies by authority
}

[jrochkind]

This would be a backwards-incompat change for current users of qa.

Maybe a transition period, where the current responses are still available at the current paths, backwards-compatibly, but there's another path where the json-api responses could be retrieved from?