feat(auth): implement user authentication system

backend/node_modules/mysql2/lib/packets/auth_switch_response.js

@@ -0,0 +1,30 @@
+'use strict';
+
+// http://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::AuthSwitchRequest
+
+const Packet = require('../packets/packet');
+
+class AuthSwitchResponse {
+  constructor(data) {
+    if (!Buffer.isBuffer(data)) {
+      data = Buffer.from(data);
+    }
+    this.data = data;
+  }
+
+  toPacket() {
+    const length = 4 + this.data.length;
+    const buffer = Buffer.allocUnsafe(length);
+    const packet = new Packet(0, buffer, 0, length);
+    packet.offset = 4;
+    packet.writeBuffer(this.data);
+    return packet;
+  }
+
+  static fromPacket(packet) {
+    const data = packet.readBuffer();
+    return new AuthSwitchResponse(data);
+  }
+}
+
+module.exports = AuthSwitchResponse;