The verification has been cancelled, by us or the other side.
The payload is either an Error, or an (incoming or outgoing) MatrixEvent, depending on unspecified reasons.
The user should confirm if the other side has scanned our QR code.
The payload is the ShowQrCodeCallbacks object.
SAS data has been exchanged and should be displayed to the user.
The payload is the ShowSasCallbacks object.
Events emitted by Verifier