I'm trying to subscribe to the promotable_posts endpoint of the Facebook page to get updates for unpublished and hidden posts ("dark posts"). According to Facebook it should be possible to subscribe to that endpoint: https://developers.facebook.com/docs/pages/realtime#data
But that endpoint is not listed on https://developers.facebook.com/apps/[APP_ID]/webhooks/ and I can't add the subscription of the endpoint via the API either. It's working for endpoints like feed.
How can I subscribe to that endpoint? And how can I get hidden posts? Normally I would use https://graph.facebook.com/[PAGE_ID]/promotable_posts?include_hidden=true&access_token=... to get those posts when I'm polling, but I can't tell Facebook to include hidden posts when I subscribe to an endpoint.
The Facebook documentation is wrong: You don't have to subscripe to "promotable" posts to get unpublished posts and you don't have to do anything else to get "hidden" posts.