Interface for calls which may be muted. This only makes sense for channels where audio or video is streaming between members.
Muting a call content indicates that the user does not wish to send outgoing audio or video.
It should always be possible to mute an entire call. It is sometimes also possible to mute individual Contents (e.g. to prevent background noise from disturbing other participants, but remain visible on webcam) or to mute individual streams (e.g. to "whisper" to other call participants)
Inform the CM that the Call, Content or Stream should be muted or unmuted.
The CM will tell the streaming implementation to Mute Streams as
required, and emit