Release version 2.4.0

Major features:
* Support for new use case and feature settings has been added.

Minor features and changes:
* New API endpoints have been added to reduce requests on session
  imports.
* Session use case and feature settings are now included in exports and
  imports.
* Authentication providers can now be enabled separately for students
  and lecturers.
* A new suspended votes offset setting has been added.
* JSON export and import now include session info and feature settings.

Bug fixes:
* Deleted sessions are now correctly evicted from cache.
* Answer count calculation for free text questions has been fixed.
This tag has no release notes.