Upgrade an existing Flask web app

I have a small app with three input screens. The inputs are currently collected via [login to view URL] and stored into a session dict that is sent between flask and the html pages. The html pages use jinja2, e.g. to build the right number of input fields. Further, the sessions can be saved into an sqlite db and loaded later on. I need the following three tasks: - Include a log-in page and make sure that sites are only available to registered users. - Include proper form management, e.g via WTForms, so that input fields are consistently filled if input is available from previous entry (e.g. when user goes back to previous screen). - Currently I send the session dict between Flask and html back and forth. I think, best practice is to only have a session-id in the session and then store the full dict in a (temporary) DB. This I also want to include.