make user agent header configurable through env variable

app/config/appConfig.js

@@ -41,6 +41,10 @@ const PROSTOR_LOGIN = {
   PASSWORD: process.env.PROSTOR_LOGIN_PASS
 };
 
+const USER_AGENT =
+  process.env.USER_AGENT ||
+  "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36";
+
 module.exports = {
   APP_PORT,
   APP_URL,
@@ -54,5 +58,6 @@ module.exports = {
   API_MAP_KEY,
   STAGING,
   CHECK_UP_DAYS,
-  PROSTOR_LOGIN
+  PROSTOR_LOGIN,
+  USER_AGENT
 };