feat: Convert helpers to use JS files

packages/backend/src/helpers/create-auth-token-by-user-id.js

@@ -0,0 +1,14 @@
+import jwt from 'jsonwebtoken';
+import appConfig from '../config/app';
+
+const TOKEN_EXPIRES_IN = '14d';
+
+const createAuthTokenByUserId = (userId) => {
+  const token = jwt.sign({ userId }, appConfig.appSecretKey, {
+    expiresIn: TOKEN_EXPIRES_IN,
+  });
+
+  return token;
+};
+
+export default createAuthTokenByUserId;