type Dns::Zoneentry = Struct[{
    mname         => String,
    rname         => String,
    ns            => Optional[Array[String]],
    records       => Optional[Array[Dns::Recordentry]],
    update_policy => Optional[String],
    refresh       => Optional[Dns::Ttl],
    retry         => Optional[Dns::Ttl],
    expire        => Optional[Dns::Ttl],
    negative_ttl  => Optional[Dns::Ttl],
    ttl           => Optional[Dns::Ttl],
}]