Support event name on web hooks

[PhilippeVienne]

Type of PR: Bug resolution
Kind of bug: Null pointer on web hook event types
Solution: https://stackoverflow.com/questions/33611199/jackson-jsontypeinfo-property-is-being-mapped-as-null

It allows the following usage:

    @Override
    public void onProjectEvent(ProjectSystemHookEvent event) {
        switch (event.getEventName()) {
            case ProjectSystemHookEvent.PROJECT_CREATE_EVENT:
                log.info("Project created {}", event.getName());
                break;
            case ProjectSystemHookEvent.PROJECT_DESTROY_EVENT:
                log.info("Project destroyed {}", event.getName());
                break;
        }
    }

[gmessner]

@PhilippeVienne
Nice find. I have merged the PR, will include on the next release which should be in the next 1-2 days.

I have to say Jackson sure picked an unusual way to do this, not passing a field down to the deserializer by default because it was used in type selection seems a bit odd, It does indicate this as the behavior if you thoroughly read the Javadocs on @JsonTypeInfo (https://fasterxml.github.io/jackson-annotations/javadoc/2.9/com/fasterxml/jackson/annotation/JsonTypeInfo.html), they should consider making visible true by default, as many people have run into this problem.