OPTIONS should expose headers

Closes #38

Author: Ben Stahl

lib/handlers/OptionsHandler.js

@@ -20,6 +20,8 @@ class OptionsHandler extends BaseHandler {
         // Preflight request
         res.setHeader('Access-Control-Allow-Methods', ALLOWED_METHODS);
         res.setHeader('Access-Control-Allow-Headers', ALLOWED_HEADERS);
+        res.setHeader('Access-Control-Expose-Headers', ALLOWED_HEADERS);
+
         res.setHeader('Access-Control-Max-Age', MAX_AGE);
 
         if (this.store.extensions) {

test/Test-OptionsHandler.js

@@ -31,6 +31,7 @@ describe('OptionsHandler', () => {
         let headers = {
             'Access-Control-Allow-Methods': ALLOWED_METHODS,
             'Access-Control-Allow-Headers': ALLOWED_HEADERS,
+            'Access-Control-Expose-Headers': ALLOWED_HEADERS,
             'Access-Control-Max-Age': MAX_AGE,
         };
         handler.send(req, res);