feat(auth): implement user authentication system

backend/node_modules/mysql2/lib/promise/inherit_events.js

@@ -0,0 +1,27 @@
+'use strict';
+
+function inheritEvents(source, target, events) {
+  const listeners = {};
+  target
+    .on('newListener', (eventName) => {
+      if (events.indexOf(eventName) >= 0 && !target.listenerCount(eventName)) {
+        source.on(
+          eventName,
+          (listeners[eventName] = function () {
+            const args = [].slice.call(arguments);
+            args.unshift(eventName);
+
+            target.emit.apply(target, args);
+          })
+        );
+      }
+    })
+    .on('removeListener', (eventName) => {
+      if (events.indexOf(eventName) >= 0 && !target.listenerCount(eventName)) {
+        source.removeListener(eventName, listeners[eventName]);
+        delete listeners[eventName];
+      }
+    });
+}
+
+module.exports = inheritEvents;