Synchronize event penalty with user penalty

[otytlandsvik]

🚨 As of now, penalties for events are saved on the event mongodb document.

This means that penalties for users on events can become out of sync with penalties on the user. This makes it impossible to for example remove someone's penalties and move them on the list if a mistake occured.

✨ Penalties should be synchronized

There is no need to double-save the penalties. They should simply be retrieved from the user when needed.