* update K8s deployment
Because `allowPrivilegeEscalation` controls SUID/SGID, we require it
when postdrop is invoked.
* correct permissions for maildrop/public
The reason our permissions previously worked out as that in setups where
SUID/SGID worked, the binaries used to place files in these directories
already have SGID set; the current set of permissions makes less sense
(as explained in this comment:
https://github.com/docker-mailserver/docker-mailserver/issues/3619#issuecomment-1793816412)
Since the binaries used to place files inside these directories alredy
have SUID/SGID set, we do not require these bits (or the sticky bit) to
be set on the directories.
* Apply suggestions from code review
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Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>
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