DefaultSerial returns a 10 digit serial based on the current day and the minute of the day.

IncrementSerial increments the given 10 digit serial by 1 if it's on the same date, otherwise the date is set to `Now().UTC()` and the counter to 0 If the counter exceeds 99, or the date part is invalid or in the future, an error is returned.

NewSerial returns a new Serial where the date is set to `Now().UTC()` and the counter to 0.

NewZone return a new, empty zone with a SOA resource record.

MX RDATA (https://tools.ietf.org/html/rfc1035#section-3.3.9).

NS RDATA (https://tools.ietf.org/html/rfc1035#section-3.3.11).

Records holds the location records for a zone.

SOA RDATA (https://tools.ietf.org/html/rfc1035#section-3.3.13).

SRV RDATA (https://tools.ietf.org/html/rfc2782).

Zone represents a DNS zone.

a record type tha implements the Equality interface can easily been checked for changes in the record.