Add Google oauth variable: hostedDomain

Which is part of `passport-google-oauth2`.
It could be used as whitelist to a domain supported by google oauth.
Ref: https://github.com/jaredhanson/passport-google-oauth2/issues/3

Signed-off-by: ike <developer@ikewat.com>

lib/config/dockerSecret.js

@@ -53,7 +53,8 @@ if (fs.existsSync(basePath)) {
     },
     google: {
       clientID: getSecret('google_clientID'),
-      clientSecret: getSecret('google_clientSecret')
+      clientSecret: getSecret('google_clientSecret'),
+      hostedDomain: getSecret('google_hostedDomain')
     },
     imgur: getSecret('imgur_clientid')
   }