* Allow leaving an MLS conversation via Wire API

* Add failing test for user leaving

* Move MLS clients to their own table

* Refactor leave action: remove list of leavers

* Update conversation object after removal

* Fix integration tests

* Implement a remote leaver test

* Update federation golden tests

* Split leave test into two

* Make removing already-removed users a no-op

* Add CHANGELOG entries

Co-authored-by: Paolo Capriotti <[email protected]>