True if the peer certificate is provided (this is always the
case for a client connection) and Certificate unifies with the
peer certificate. The example below uses this to obtain the
Common Name of the peer after establishing an https client
connection:
http_open(HTTPS_url, In, []),
ssl_peer_certificate(In, Cert),
memberchk(subject(Subject), Cert),
memberchk('CN' = CommonName), Subject)