def logstash_processor(_, __, event_dict):
    """
    Adds @version field for Logstash.
    Puts event in a 'message' field.
    Serializes timestamps in ISO format.
    """
    if 'message' in event_dict and 'full_message' not in event_dict:
        event_dict['full_message'] = event_dict['message']
    event_dict['message'] = event_dict.pop('event', '')
    for key, value in event_dict.items():
        if hasattr(value, 'isoformat') and callable(value.isoformat):
            event_dict[key] = value.isoformat() + 'Z'
    event_dict['@version'] = 1
    event_dict['_type'] = event_dict['type'] = 'feedhq'
    return event_dict