Modify the cache_peer neighbor type when passing requests
about specific domains to the peer.
Usage:
neighbor_type_domain peer-name parent|sibling domain...
For the required peer-name parameter, use either the value of the
cache_peer name=value parameter or, if name=value is missing, the
cache_peer hostname parameter.
For example:
cache_peer foo.example.com parent 3128 3130
neighbor_type_domain foo.example.com sibling .au .de
The above configuration treats all requests to foo.example.com as a
parent proxy unless the request is for a .au or .de ccTLD domain name.