IDN

This type models internationalized hostnames. An IDN provides unicode labels, a unicode string form,
and an ASCII hostname form.

A well formed IDN consists of one or more labels separated by dots. Each label may contain unicode characters
as long as the converted ASCII form meets the requirements of RFC1123 (e.g., 63 or fewer characters and no
leading or trailing dash). A dot is represented as an ASCII period or one of the unicode dots: full stop,
ideographic full stop, fullwidth full stop, halfwidth ideographic full stop.

The toString method returns the IDN in the form in which it was constructed. Sometimes it is useful to
normalize the IDN -- converting all dots to an ASCII period and converting all labels to lowercase.

Note: equality and comparison of IDNs is case-sensitive. Consider comparing normalized toString values
for a more lenient notion of equality.