feat: add rest:dial metadata

specs.json

@@ -394,7 +394,8 @@
       "tag": "object",
       "to": "#target",
       "headers": "object",
-      "timeout": "number"
+      "timeout": "number",
+      "metadata": "object"
     },
     "required": [
       "call_hook",

test/jambonz-verb-test.js

@@ -258,6 +258,25 @@ test("validate correct verbs", async (t) => {
         "language" : "en-US",
         "interim": true
       }
+    },
+    {
+      "verb": "rest:dial",
+      account_sid: "1291964182631236912836123912",
+      call_hook: {
+        url: "http://127.0.0.1:3100/",
+        method: "POST",
+        username: "username",
+        password: "password",
+      },
+      from: "15583084810",
+      to: {
+        type: "phone",
+        number: "15583084809",
+      },
+      metadata: {
+        customer: "acme",
+        referenceId: "deadbeef",
+      }
     }
   ];
   try {