Filter sessions on the DB side to check if key is available

See merge request !58

Daniel Gerhardt authored 7 years ago and Daniel Gerhardt committed 7 years ago

This should massively reduce the time needed for session creation.
Additionally, the `Transactional` annotation has been removed because
it did not have any effect in this case.

Robin Drangmeister authored 8 years ago and Daniel Gerhardt committed 8 years ago

This fixes WebSocket communication for course sessions. (dg)

Refs GH-40.

Changed `security.facebook.enabled-roles` to
`security.facebook.allowed-roles`.

Fix missing validation for MotDs

The backend wrongly trusted user input allowing the circumvention of
access control checks.

See merge request !37

The backend wrongly trusted user input allowing the circumvention of
access control checks.

The security.*.enabled properties are now loaded as booleans.

The original implementation did not correcly implement the W3C
Recommendation (https://www.w3.org/TR/2014/REC-cors-20140116/). CORS is
now implemented based the CorsFilter provided by Spring MVC.

Origins allowed for CORS can now be set in the configuration.
Additionally, GET access to the following request URLs is allowed from
all origins:

* /
* /arsnova-config and /configuration/
* /statistics