Support pseudo-association merging in the UI via Solr result grouping

[kevinschaper]

We could potentially have an API endpoint that produces merged associations by means of Solr result grouping.

Result grouping in Solr only supports grouping by a single field, so we would need to concatenate values into something like:

f"{subject}-{predicate}-{object}-{negation}"

We could then group by that, with an option to drill down and view all entries in a group. This seems like it could work out be a discount version of the edge merging and evidence graph from the old system.

[monicacecilia]

Dear @mellybelly - do you have a use case or a suggestion for someone who could provide one? Thank you!