configuration test

Procfile

@@ -1 +1 @@
-web: PORT=$PORT yarn back start
+web: yarn back start

back/config/env/production/server.js

@@ -1,3 +1,5 @@
 module.exports = ({ env }) => ({
-  url: env("MY_HEROKU_URL"),
+  url: env("PUBLIC_URL", "https://fast-springs-77208.herokuapp.com"),
+  host: env("HOST", "0.0.0.0"),
+  port: env.int("PORT", 1337),
 });