This commit improves dependency management with the following changes:
- `spring-session-core`: move `javax.servlet-api` from `provided` to `optional` configuration due to introduction of reactive support
- `spring-session-data-redis`: remove Redis driver from `compile` configuration
- Boot samples: delegate Redis driver choice to `spring-boot-starter-data-redis`
- polish `test` configuration dependencies
This commit improves existing Hazelcast support, which is based on
MapSessionRepository, with dedicated HazelcastSessionRepository
that implements the FindByIndexNameSessionRepository contract.
Also a new hazelcast-spring-session module was added to provide
dependency management for Hazelcast support.
Fixes gh-544
