This attribute holds a nonce to be used in the HTTP Digest
The RADIUS server MAY put a Digest-Nextnonce Attribute into an
Access-Accept packet. If this attribute is present, the RADIUS
client MUST put the contents of this attribute into the
nextnonce directive of an Authentication-Info header in its
HTTP-style response. This attribute MUST only be used in
107 for Digest-Nextnonce
It is recommended that this text be base64 or hexadecimal data.