on
Called when end-to-end encryption starts working or fails on one of this participant's streams.
Decryption failures are not reported yet: a wrong or removed key shows only as the stream going dark.
Encryption states are reported on the local participant, decryption states on the remote sender.
Parameters
stream
the stream concerned. If the SDK cannot match the reported ID it substitutes another stream of the same RTCStream.kind, so trust RTCStream.kind over RTCStream.id here.