No subject

reindexing all of the records by iterating over all of the unique
values of source in msfe and populating an additional row containing
the union of the subject terms for each source record. Once that's
complete, insert the new config.metabib_field entry and the system
would be golden.

If there's a better way of solving this problem, that would be great,
as adding the //mods32:mods/mods32:subject//text() xpath means that
we're effectively indexing all subject terms twice if we keep the
existing temporal / topic / geographic subject indexes as well.  Maybe
instead of adding the xpath, we could populate a view or use rules to
maintain an additional row based on a union of all subject terms for a
given record? Just brainstorming in a slightly sick fashion. But in
the short term, that slight additional bloat seems like a small price
to pay for making subject searches work the way that our users appear
to expect them to work.