allow target-level headers on outdials (#29)

lib/tasks/specs.json

@@ -338,6 +338,7 @@
         "type": "string",
         "enum": ["GET", "POST"]
       },
+      "headers": "object",
       "name": "string",
       "number": "string",
       "sipUri": "string",

lib/utils/place-outdial.js

@@ -60,10 +60,16 @@ class SingleDialer extends Emitter {
     opts.headers = opts.headers || {};
     opts.headers = {
       ...opts.headers,
+      ...(this.target.headers || {}),
       'X-Jambonz-Routing': this.target.type,
-      'X-Jambonz-FS-UUID': srf.locals.fsUUID,
       'X-Call-Sid': this.callSid
     };
+    if (srf.locals.fsUUID) {
+      opts.headers = {
+        ...opts.headers,
+        'X-Jambonz-FS-UUID': srf.locals.fsUUID,
+      };
+    }
     this.ms = ms;
     let uri, to;
     try {