Specifies endpoints and which streams (audio and/or video) they receive. Supports the following keys:
- remoteParticipantId as the key containing one or more endpoint IDs.
- The keyword 'all' for all the endpoints in a conference. You can additionally specify the 'new' key for all the newly connected endpoints. IMPORTANT: 'all' excludes all other keys except for 'new'. If 'all' and remoteParticipantId are both specified, the latter will be ignored.