Add att_xfer_destination_number variable to indicate the original destination…

Add att_xfer_destination_number variable to indicate the original destination number of the attended transfer leg on REFER for semi-attended transfer scenarios.

src/mod/endpoints/mod_sofia/sofia.c

@@ -6731,10 +6731,12 @@ void sofia_handle_sip_i_refer(nua_t *nua, sofia_profile_t *profile, nua_handle_t
 							if ((a_session = switch_core_session_locate(br_a))) {
 								const char *moh = profile->hold_music;
 								switch_channel_t *a_channel = switch_core_session_get_channel(a_session);
+								switch_caller_profile_t *prof = switch_channel_get_caller_profile(channel_b);
 								const char *tmp;
 
 								switch_core_event_hook_add_state_change(a_session, xfer_hanguphook);
 								switch_channel_set_variable(a_channel, "att_xfer_kill_uuid", switch_core_session_get_uuid(b_session));
+								switch_channel_set_variable(a_channel, "att_xfer_destination_number", prof->destination_number);
 
 								if (profile->media_options & MEDIA_OPT_BYPASS_AFTER_ATT_XFER) {
 									switch_channel_set_flag(a_channel, CF_BYPASS_MEDIA_AFTER_BRIDGE);