The SDK-internal global id of the recipient (userGUID). Stable across the
main session and all subsessions.
The developer-supplied external key of the recipient (the userIdentity
passed when the user joined). Stable while the user stays in the session.
Address a specific recipient of a command channel message.
userKeyanduserGuidcan locate the same user across the main session and subsessions, so they can be used to message a user in a different session. A recipient and a broadcast scope are mutually exclusive.