Internal
Send all necessary events to make this user leave the RTC session.
the maximum duration in ms until the promise is forced to resolve.
It resolves with true in case the leave was sent successfully. It resolves with false in case we hit the timeout before sending successfully.
Call this if the MatrixRTC session members have changed.
This interface defines what a MembershipManager uses and exposes. This interface is what we use to write tests and allows to change the actual implementation Without breaking tests because of some internal method renaming.