Persistent storage of data from session

[Baschdl]

We need to persistent store the data from the session object because otherwise it gets discarded after we reach the limit of 500 saved session objects.

[MkuuWaUjinga]

In general whenever a user finishes rating, a json-file will be created and stored somewhere else. So this data is safe. I think it is quite unrealistic that 500 people will rate at the same time at the KDD-day. In server.py logout, the session is closed, but I couldn't really find out what exactly it does 😆

[MkuuWaUjinga]

working on redis for session management