Value: You can relay streams to a CDN, transcode streams, or publish streams to an RTC room. Select the mode that fits your needs.
Note: If you need to use more than one publishing mode,
you can call startPublishMediaStream multiple times and set TRTCPublishTarget to a different value each time.
You can use one mode each time you call the startPublishMediaStream API. To modify the configuration, call updatePublishCDNStream.
