`aem` `aio-aem-events-osgi-mapping` : Cannot make custom Event Handler Type

### Question
How to make a custom Event Handler that will be registered and has an additional custom field in the event's request payload?

### Expected Behaviour
We want a custom Page Publish event which has custom fields in the event's request payload.

1. Create **com.adobe.aio.aem.event.osgimapping.internal.OsgiEventMappingSupplierImpl-custom.cfg.json** file in config.author directory containing the following:

{
"aio.event.code": "custom_published",
"aio.event.label": "Custom Page Published",
"aio.event.description": "Custom Page Published Event",
"aio.xdm.event.type": "com.adobe.xdm.event.AemPagePublishedEvent",
"osgi.event.handler.type": "com.proj.core.eventhandler.CustomHandler",
"osgi.topic": "com/day/cq/replication",
"osgi.filter": "(&(type=ACTIVATE)(!(event.application=*)))",
"osgi.jcr.path.filter": "/content/"
}

2. CustomHandler inherits from one of the abstract classes like ReplicationEventHandler (and puts CustomPage inheriting from Page) or something else which will give access to add custom fields to the event's request payload.
3. Handler is registered and the event's request payload has defined by CustomHandler additional fields.

### Actual Behaviour
1) When tried to inherit from **ReplicationEventHandler\** (where CustomPage inherits from com.adobe.xdm.content.Page) and **AdobeIoEventHandler\**, there was a problem, because **List> getXdmObjectActorDateTriples(Event event, ResourceResolverWrapper resourceResolverWrapper)** is package-private and there cannot be a class created outside this package and implements this method.
2) When inheriting eg. from **PageReplicationEventHandler** custom handler does not work and logs say:

com.adobe.aio.aem.event.osgimapping.internal.OsgiEventMappingRegistrationServiceImpl Adobe I/O Events' OSGI Handler Registration failed: `Unreferenced/unimplemented OSGI event Handler value: com.proj.core.eventhandler.CustomHandler
com.adobe.aio.exception.AIOException: Unreferenced/unimplemented OSGI event Handler value: com.proj.core.eventhandler.CustomHandler

Empieza leyendo OsgiEventMappingSupplierImpl y OsgiEventMappingRegistrationServiceImpl; después, sigue cómo se reconocen PageReplicationEventHandler y ReplicationEventHandler. Revisa el método package-private getXdmObjectActorDateTriples y el error de handler no referenciado. Se considera terminado cuando un handler personalizado puede registrarse a partir del mapping mostrado y añadir campos al payload de la solicitud del evento.

Escrito por el modelo de indexación a partir del texto del issue.