ae2aa8b6d1
JIRA: https://jira.spring.io/browse/INT-4440 The previous fix eliminated an extra `generateId()` call, but at the same introduced regression do not populate `id` and `timestamp` from the serialized state, e.g. after JSON transferring over the network * Introduce a couple utility methods in the `MutableMessageHeaders` to extract and parse `id` and `timestamp` from the provided headers **Cherry-pick to 5.0.x**