Fixing #1900 JS SDK file upload (#1935)

* Fixing #1900 JS SDK file upload

JS SDK file upload uses req.body._ContentType to specify the upload content type

* Fixing import statements

* Dont clear the cache just delete the new entry that the test added.

* adding E2E test for _ContentType support

src/middlewares.js

@@ -84,6 +84,10 @@ function handleParseHeaders(req, res, next) {
         info.masterKey = req.body._MasterKey;
         delete req.body._MasterKey;
       }
+      if (req.body._ContentType) {
+        req.headers['content-type'] = req.body._ContentType;
+        delete req.body_contentType;
+      }
     } else {
       return invalidRequest(req, res);
     }