Allows easy direct linking and usage of the HTML preview content
we show in the UI when viewing search results.
Note: preview_html content is a rough representation only, it does not
match exactly what was matched in the database-search-operation which
finds the results.
For #3096 and #3080
Is a little awkward, emulates a 'list' API endpoint but has unstable
paging and does not support filters/sort. This is detailed on the
endpoint though.
Made some updates to the docs system to better support parameters
and examples on GET requests.
Includes tests to cover.
For #909