This feature extracts a value from the p-visited-network-id header(s) that is to be included in registration data.
The p-visited-network-id header is defined in http://www.ietf.org/rfc/rfc3455.txt
The P-Visited-Network-ID header field is used to convey to the registrar or home proxy in the home network the identifier of a visited network.
The identifier is a text string or token that is known by both the registrar or the home proxy at the home network and the proxies in the visited network.
This feature uses the value of the first p-visited-network-id header. If the value is a string then the " characters are removed.
A selection key with the platform operator and network operator set (such as OpenCloud:OpenCloud:::)
The first-party REGISTER request that was in the body of the third-party REGISTER request received by the registrar