importer: ensure metadata in DB matches prod DB rather than elasticsearch

[alisonrclarke]

The metadata in elasticsearch has enhanced fields (see document_enhancers.py) including first_author and summary_authors. It seems that imported records end up with the enhanced metadata in the DB records_metadata table, rather than what's in the production DB.

This means that imported records in our dev environment do not match what's in production, so we can miss issues when we've retrieved data from the DB instead of ES, but used the enhanced fields (e.g. #428).