As user, one can run

biber --validate_datamodel xyz.bib

Then, the log is filled with entries such as

WARN - Datamodel: report entry 'Iron2009' (oliver-kopp.bib): Missing mandatory field 'type'

A pattern for this needs to be added to

org.jabref.logic.biblog.BibtexLogParser

One can develop test driven, to first add a test to

org.jabref.logic.biblog.BibtexLogParserTest

Steps

1. Create a new @ParameterizedTest at BibtexLogParserTest for error strings and expected BibWarning. I assume @MethodSource will be needed. Add the above test string and result
2. Adapt BibtexLogParser

No need to create a new .blg file for testing; this is too much effort.