The Subject field is a Distinguished Name. oid-registry defines the OIDs for expected attributes, and this crate defines additional abbreviations for use when printing them in an X509Name. Unfortunately, both this and oid-registry are missing 0.9.2342.19200300.100.1.1 (oid-info.com), which is "uid" (or, as an abbreviation for printing, "UID").
I'm filing it here as the actual issue is printing X509Names, though it should also be added to oid-registry for good measure.