schema:             MNTNER-SCHEMA
ref:                dn42.mntner
key:                mntner         required  single    primary schema
key:                descr          optional  single
key:                mnt-by         required  multiple  lookup=dn42.mntner
key:                admin-c        optional  multiple  lookup=dn42.person,dn42.role
key:                tech-c         optional  multiple  lookup=dn42.person,dn42.role
key:                auth           optional  multiple  > [method] [value]...
key:                org            optional  multiple  lookup=dn42.organisation
key:                abuse-mailbox  optional  single
key:                sha512-pw      optional  single
key:                remarks        optional  multiple
key:                source         required  single    lookup=dn42.registry
mnt-by:             DN42-MNT