DirectoryString is a CHOICE type and therefore uses explicit tagging

DirectoryString is a CHOICE type and therefore uses explicit tagging

EDIPartyName has 2 fields that use a DirectoryString. However they were
marked as implicit tagging - which is not correct for a CHOICE type.

Additionally the partyName field was marked as Optional when, according to
RFC5280 it is not.

Many thanks to github user @filipnavara for reporting this issue. Also to
David Benjamin from Google who independently identified and reported it.

Fixes #6859

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>