feat: auto choose speech synthezier from account/service level for createCall (#60)

* feat: auto choose speech synthezier from account/service level

* wip: add integration test

* fix: review comment

* fix: review comment

test/feature-server-test-scaffold/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "webhook",
+  "version": "1.0.0",
+  "description": "simple webhook app for test purposes",
+  "main": "app.js",
+  "scripts": {
+    "start": "node app"
+  },
+  "author": "Dave Horton",
+  "license": "MIT",
+  "dependencies": {
+    "express": "^4.17.1",
+    "uuid": "^8.3.2"
+  }
+}