Authentication on `https://appstoreconnect.apple.com/iris/v1`

Hi,

I've tried to authenticate this endpoint https://appstoreconnect.apple.com/iris/v1/betaFeedbacks with the JWT token as described in the documentation, but it's not working. I know this endpoint is not documented, but gathering the beta feedback and being able to extract it to some ticket system (e.g. GitHub board) would be a really helpful option for us.

Does anyone know how we can authenticate this one?