Fix crash with express 5

express.json does not enforce json. this means it will pass it through
but let req.body be undefined. this causes all our asserts to crash

src/middleware/index.js

@@ -3,6 +3,7 @@
 exports = module.exports = {
     cookieParser: require('cookie-parser'),
     cors: require('./cors.js'),
+    json: require('./json.js'),
     lastMile: require('connect-lastmile'),
     multipart: require('./multipart.js'),
     timeout: require('connect-timeout')

src/middleware/json.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const express = require('express');
+
+function _mime(req) {
+  const str = req.headers['content-type'] || '';
+  return str.split(';')[0];
+}
+
+exports = module.exports = function (options) {
+    const json = express.json(options);
+
+    return function (req, res, next) {
+        // enforce json body type. without this the json middleware will skip parsing and req.body might be undefined
+        if (_mime(req) !== 'application/json') return res.status(400).send('incorrect mime type. expecting application/json');
+        json(req, res, next);
+    };
+};