Add config.js, dockerfile

server/src/config.js

@@ -0,0 +1,13 @@
+function get(key, defaultValue) {
+  const value = process.env[key]
+  if (value != null) {
+    return value
+  }
+  return defaultValue
+}
+
+export default {
+  host: get('HOST', 'localhost'),
+  port: get('PORT', 3000),
+  db: get('MONGO_URL', 'mongodb://localhost:27017/odyssey-test'),
+}