[itaifrenkel]

Two comments on effectively once stream processing.

1. Consider adding an example for a stateful event stream processor client that saves the last read stream offset in redis, together with its current state and continues reading from that offset as an atomic operation. For example, a client that sums a stream of numbers, in order to have effectively once semantics would need to persist to redis the sum and offset together.

2. Consider adding a stream read deduplication example to mitigate clients that reinserted the same event twice. It is not clear how the client should behave if it didn't get an ack and it resents an event. What is the correct resending semantics so the reader would effectively dedup? What is the right data structure used to dedup message ids without consuming too much memory, etc...?