Convert backend code to ES modules

Bundling code now with Rollup for its flat bundling and tree shaking
support. Front end code still goes through Webpack for browser support.

lib/auth.js

@@ -18,9 +18,9 @@
  */
 "use strict";
 
-const crypto = require("crypto");
+import { createHash } from "crypto";
 
-function parseAuthHeader(authHeader) {
+export function parseAuthHeader(authHeader) {
   authHeader = authHeader.trim();
   const method = authHeader.split(" ", 1)[0];
   const res = { method: method };
@@ -53,11 +53,11 @@ function parseAuthHeader(authHeader) {
   return res;
 }
 
-function basic(username, password) {
+export function basic(username, password) {
   return "Basic " + Buffer.from(`${username}:${password}`).toString("base64");
 }
 
-function digest(username, password, uri, httpMethod, body, authHeader) {
+export function digest(username, password, uri, httpMethod, body, authHeader) {
   const cnonce = "0a4f113b";
   const nc = "00000001";
   let qop;
@@ -68,7 +68,7 @@ function digest(username, password, uri, httpMethod, body, authHeader) {
     else qop = authHeader.qop;
   }
 
-  let ha1 = crypto.createHash("md5");
+  let ha1 = createHash("md5");
   ha1
     .update(username)
     .update(":")
@@ -78,7 +78,7 @@ function digest(username, password, uri, httpMethod, body, authHeader) {
   // TODO support "MD5-sess" algorithm directive
   ha1 = ha1.digest("hex");
 
-  let ha2 = crypto.createHash("md5");
+  let ha2 = createHash("md5");
   ha2
     .update(httpMethod)
     .update(":")
@@ -86,7 +86,7 @@ function digest(username, password, uri, httpMethod, body, authHeader) {
   if (qop === "auth-int") ha2.update(":").update(body);
   ha2 = ha2.digest("hex");
 
-  const hash = crypto.createHash("md5");
+  const hash = createHash("md5");
   hash
     .update(ha1)
     .update(":")
@@ -113,7 +113,3 @@ function digest(username, password, uri, httpMethod, body, authHeader) {
 
   return authString;
 }
-
-exports.parseAuthHeader = parseAuthHeader;
-exports.basic = basic;
-exports.digest = digest;