improve HazelcastSessionRepository connection exception handling

The current implementation of HazelcastSessionRepository does not handle any HazelcastException when accessing the sessions map.

In the case of a hazelcast server connection lost, this causes all requests to return 500 error status.

The reason for this is the SessionRepositoryFilter calls the HazelcastSessionRepository early in the request cycle which throws an Exception when accessing the sessions IMap.

Since the HazelcastSession is only visible in the package i had to completely replace the current HazelcastSessionRepository with my own implementation to add additional exception handling.

Example code for Hazelcast Exception Handling:

 @Override
    public HazelcastSession findById(String id) {

        try {
            MapSession saved = this.sessions.get(id);
            if (saved == null) {
                return null;
            }
            if (saved.isExpired()) {
                deleteById(saved.getId());
                return null;
            }
            return new HazelcastSession(saved);
        } catch(HazelcastException e){
            LOG.error("hazelcast session failed to find", e);

            return null;
        }
    }

I've added a try catch around every this.sessions access. I'm not sure if this is the right approach i would appreciate any better suggestions to prevent this situation. Thanks in advance.

Review HazelcastSessionRepository and the SessionRepositoryFilter interaction described in the issue, focusing on every access to the sessions IMap and the HazelcastException behavior. Determine the intended behavior when the Hazelcast connection is lost, then add or update coverage so requests do not fail with a 500 response in that situation.