These can be tested by adding a `Task.Delay(3000);` at the end of the
`MultiplayerClient.JoinRoom` task. The reason is typically that
`Client.Room` becomes not-null but the join task still hasn't completed
yet, so e.g. the ready button is still disabled.
It needs to be explicitly stated that the users in this list are related
to the *joined* room. Especially since it's sharing its variable name
with `SpectatorStreamingClient` where it has the opposite meaning (is a
list of *globally* playing players).
