Session Management

[maany]

Auto logout user when rucio token expires.
Test that the correct user is always set as active user in the session

[maany]

@ThePhisch we would have to add a header/banner to the login page. If a user is logged into multiple accounts, they should be able to switch to a valid account using the banner even from the login page.

Since #362, the middleware will redirect the user to the login page, if the currently active account has an invalid token. In the scenario where multiple accounts were present in the session, the middleware does not switch the user to a particular account. It is up to the frontend to get the user to either login to the account where the invalid rucio auth token was found or select another account