Enable views filtering on registration_entity.status

I've tried to implement this, specifically filtering based on registration_entity.status, but it's beyond my knowledge level. I defined a filter, and extended views_handler_filter_boolean_operator in its handler, but I just end up filtering based on node.status.

I can't be the first to want to filter nodes with registration entities in this way, so perhaps there is a way to accomplish this through the ui, with the existing tools, that I am overlooking?