Add dfid_document_type for research outputs
Add dfid_document_type for research outputs

e.g. Conference Paper, Book Chapter. Single-valued.

alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild,alphagov/specialist-publisher,alphagov/specialist-publisher,alphagov/specialist-publisher-rebuild