tldGetBaseDomain
Finds the base domain for a given @hostname
The base domain is composed by the top level domain (such as .org, .com, .co.uk, etc) plus the second level domain, for example for myhost.mydomain.com it will return mydomain.com.
Note that null will be returned for private URLs (those not ending with any well known TLD) because choosing a base domain for them would be totally arbitrary.
Prior to libsoup 2.46, this function required that @hostname be in UTF-8 if it was an IDN. From 2.46 on, the name can be in either UTF-8 or ASCII format (and the return value will be in the same format).
Return
a pointer to the start of the base domain in @hostname. If an error occurs, null will be returned and @error set.
Parameters
hostname
a hostname