feat(auth): implement user authentication system

backend/node_modules/mysql2/lib/pool_connection.js

@@ -0,0 +1,12 @@
+'use strict';
+
+const BasePoolConnection = require('./base/pool_connection.js');
+
+class PoolConnection extends BasePoolConnection {
+  promise(promiseImpl) {
+    const PromisePoolConnection = require('./promise/pool_connection.js');
+    return new PromisePoolConnection(this, promiseImpl);
+  }
+}
+
+module.exports = PoolConnection;