add param:confirm-blind-transfer var:confirm_blind_transfer that makes blind transfers keep the transferrer on the line until its confirmed that the call was completed or brings it back to the bridge. blind_transfer_ack app can be executed in the dp by the transferee to indicate sucess or fail or a sucessful bridge will automatically trigger a success

src/mod/endpoints/mod_sofia/mod_sofia.h

@@ -264,6 +264,7 @@ typedef enum {
 	PFLAG_PRESENCE_MAP,
 	PFLAG_OPTIONS_RESPOND_503_ON_BUSY,
 	PFLAG_PRESENCE_DISABLE_EARLY,
+	PFLAG_CONFIRM_BLIND_TRANSFER,
 	/* No new flags below this line */
 	PFLAG_MAX
 } PFLAGS;