Load HP-MP mappings into SSSOM Solr index at ingest build time

[kevinschaper]

So that we see HP-MP mappings on the page, we should download them and bring them in as part of the KG build. It's important that we not feed these mappings to the merge (we don't want to merge the nodes!), but we can download them and pass them into the Solr load.

[kevinschaper]

This is blocked, we need an improved display of SSSOM mappings so that we don't turn the other side of all mappings into external links (in some cases, like MP-HP, there are SSSOM mappings to nodes that are in the graph, so we want internal links).