API/SDK support for direct calls between contacts

Background is here:

At a minimum it would be nice if the REST API supported the ability to trigger the same incoming call notification that the desktop app can trigger. Without this, the alternative would be sending a chat message to you contact with a link to your meeting room.

Might also need a webhook to be notified when one of these notifications come in through the REST API so 3rd party applications have a way to receive this notification.

Even better would be if the native SDKs supported direct calling between contacts! But for that to happen, the SDKs would also have to support retrieval of contacts.