Hello,

I would like to contribute a ValidatingEntityCallback (in addition to the ValidatingMongoEventListener) to the code base.

The ValidatingMongoEventListener is not suitable for me due to the design nature of EventListener and EntityCallback. I prefer EntityCallback

IMHO the ValidatingMongoEventListener should (even) be marked as deprecated, because

• the EntityCallbacks are recommended by the Spring docs and
• EventListener are by design triggered/executed before any EntityCallback. This can lead to undesired behaviour difficult to track down by a developer, e.g. validation of entity happens before the entity in request is manipulated by any EntityCallback

If the maintainers/team accept my enhancement proposal, I can make a pull request.