NethVoice: add 302 header handling

[andrea-marchionni]

I know that some VoIP operators (for example TWT), allow the use of the SIP 302 option, which enables the switchboard to divert a call to an external number, and the latter displays the real number of the caller and not that of the line that the switchboard is using to divert the call.

It could enable forward from NethVoice CTI using this option via Phone lines and announcements giving the possibility to use this option.

Some notes:

1. add a context in the file /etc/asterisk/extensions_custom.conf that contains:

[transfer-using-refer]
exten => _X.,1,Transfer(PJSIP/sip:${EXTEN}@TrunkName)

2. create a Custom destination that in the Target field contains:

transfer-using-refer,<TransferRecipientNumber>,1

3. Enter the custom destination as the recipient of the transfer.

4. In the Advanced imports of the route that uses the custom destination it is important to Disable the Force Answer

To insert this thing into the configuration we were considering doing it this way:

https://www.3cx.it/blog/voip-comefare/deviazione-opzione-sip-302-parte-2/

Or alternatively create a general setting that then creates all the user deviations in this mode so that users who activate deviation on NethVoice CTI also use this mode.