Add test where a client has multiple chatroom and it deletes a

one-on-one first and then another client deletes a group chat. After each deletion, all the clients will try to send multiple messages to every chatroom they are in

Do to increase explicitely event reference count in participant device as it is already done by the shared_ptr libc implementation

Create EventSubscribe C++ object when receiving a SUBSCRIBE instead of calling the C API and taking a reference in the C side

When a participant device is removed from a chatroom, make sure the server doesn't end the subscription if it applies to a set of chatrooms. Doing so will have detrimental consequences on all remaining chatrooms that receive events through this subscription and it will prevent clients from sending messages to any encrypted chatrooms covered by the ended SUBSCRIBE dialog.