refactor(app.js): Extract tooBusy

lib/web/middleware/tooBusy.js

@@ -0,0 +1,13 @@
+'use strict'
+
+const toobusy = require('toobusy-js')
+
+const response = require('../../response')
+
+module.exports = function (req, res, next) {
+  if (toobusy()) {
+    response.errorServiceUnavailable(res)
+  } else {
+    next()
+  }
+}