How to get a list of users subscribed to a MR through API?

Where can I get the information about users who are subscribed to a MR (i.e. those who have the “Notifications” toggle enabled)? In the API documentation on MRs there is only an endpoint to (un)subscribe the current user, but nowhere do I see the list of subscribed users.

I can see a list of reviewers, assignees and participants, but none of those contain all of the subscribed users.

I am writing a small bot/webhook relay to send notifications to our users and this is much needed.

Thank you