fun getPresences(withoutAvatar: Boolean, onCompletion: (Either<List<Presence>, SippoResourceError>) -> Unit): Unit
Fetches all the presences to which the current user is subscribed.
withoutAvatar - True if you want to recover the presences without the avatar and false otherwise.
onCompletion - Callback that will be invoked when the request is completed.
It will receive the presence list in case of success or a SippoResourceError otherwise.