Warm line feature missing

[sawik-PL]

short description
I see no way to setup warm line - a number/extension dialled some time after (taking handset off-hook or pressing "new call" or pressing line button) with no digit pressed. There is a hotline feature (or adhocnumber) but it's something different.

The solution
I've implemented the feature, patch attached.

chan-sccp version: (include revision and/or branch if relevant)
latest today (4.3.5)

asterisk version: (include revision and/or branch if relevant)
tested with 18.18.0
warmline.diff.txt