Fixes https://github.com/spring-projects/spring-integration/issues/3226 * Redis stream message handler support. * This is the outbound part publishing message to the actual stream using ReactiveStreamOperations * Addition of more test cases with one using `MessageChannel`. * Improvements after PR review. * Removed failed test reading List from a Stream * Code style clean up * Remove `rawtypes` usage * Remove redundant inner classes for test model * Add `What's New` note