Thank you for your feedback. I wanted to focus on on keeping the scope of the project small. Yes, using NextAuth is an option. And it may be something we can cover in the future. I wanted to show basic auth implementation without using a library.
I know some folks like to you different Auth provides, like Clrek and many others. So wanted to keep this part open for folks to chose later if they want to implement other auth libraries.
But great point. And for any one interested, checkout the docs here to learn more about NextAuth
Also here is another great resource an authentication in general.