JIRA: https://jira.spring.io/browse/INT-3338 INT-3338: Add Docs INT-3338: Make `priority` 'smart' Add `Sort` for all group queries dependently of `priorityEnabled`. Avoids the need to configure separate collections for different type of `MessageStore` INT-3338: Add `MongoDbChannelMessageStore` INT-3338: Polishing, Fixes, Improvements Doc Polishing Fix stream test.