standardised the api response, updated contribute

server-node/src/utils/endpoint-utils.js

@@ -0,0 +1,9 @@
+
+export function respondWithBinaryPdf(res, buffer, filename) {
+    res.writeHead(200, {
+        'Content-Type': "application/pdf",
+        'Content-disposition': 'attachment;filename=' + filename,
+        'Content-Length': buffer.length
+    });
+    res.end(Buffer.from(buffer, 'binary'))
+}