NAPTR-Pattern is an optional parameter that specifies a regexp
that will be used to match the contents of NAPTR records during Resolver
service discovery.
If NAPTR-Pattern is defined and matches a NAPTR
DNS record, it will be used to determine the protocol and transport to be
used. The regexp is expected to match 2 substrings. The first is the
protocol and can be 'radsec' or 'radius'. The second is the transport to
use, and can be 'tls', 'tcp' or 'udp'.