Investigate using Lua scripts in Redis session repositories

[vpavic]

The Redis session repository implementations are currently not executing data store operations atomically, which can be challenging to deal with in highly concurrent environments where race conditions are common. It also requires multiple roundtrips to Redis server in order to complete what is a logical session repository operation.

We could look into modeling our operations as Lua scripts, similarly like for instance Spring Integration's RedisLockRegistry does. See also reference on Redis EVAL command.