#4, добавила middleware для аутентификации пользователя

middleware/auth.js

+const User = require("../models/User");
+
+const auth = async (req, res, next) => {
+  const token = req.get("Token");
+  if (!token) {
+    return res.status(401).send({error: "Token was not presented"});
+  }
+  const user = await User.findOne({token});
+  if (!user) {
+    return res.status(401).send({error: "You must be logged in!"});
+  }
+
+  req.user = user;
+  next();
+};
+
+module.exports = auth;