The messages in a schedule (RecurringMessage) are created at compile time, per Trigger. This means a trigger will always give the same message. This limits the usefulness of the component, because messages can often be dynamic. E.g. with a specific payload from the database or with a Uuid per message (often the case with architectures like EventSourcing / cqrs).
Also there is no way for a trigger to only 'check' what the getNextRunDate is, without always triggering a message.

This PR makes it possible to yield zero or more messages when a trigger is triggered. Due to the trigger being a method, the messages can be created at runtime, with a unique payload (or directly serving messages from a DB table).
Since the component is still experimental in 6.3, it's probably good to get something like this in before 6.4 is released.