initial support for conference and queues

lib/middleware.js

@@ -10,7 +10,7 @@ module.exports = function(srf, logger) {
   const {lookupAppByPhoneNumber, lookupAppBySid, lookupAppByRealm}  = srf.locals.dbHelpers;
 
   function initLocals(req, res, next) {
-    const callSid = uuidv4();
+    const callSid = req.has('X-Retain-Call-Sid') ? req.get('X-Retain-Call-Sid') : uuidv4();
     req.locals = {
       callSid,
       logger: logger.child({callId: req.get('Call-ID'), callSid})