Now, it's the time to add authentication to our website.

• Use a server-side session to store the user's state (e.g., an authenticated bool + username string keys).
  • Don't forget to set a secret_key for the session, otherwise it won't work!
• Write the Flask functions for /login and /logout with the appropriate checks / actions.
• You can either use the included login.html template page, or roll out your own!
  • Check out the input names inside the <form>!
• Hint: you can also set the authenticated variable inside the Jinja template to conditionally display the user's status.
  • You can use a Flask context processor to avoid needless code duplication;
  • Alternative: the session is readily available inside Jinja2 templates!