Add a new player-info event to the stream

Add a new player-info event to the stream

This event informs the player what their ID and their name is. It's
significant to tell them their own name because it may be provided
from the server session (obtained by a cookie from the client).

This commit includes a test case which uses the existing /profile
endpoint to set a name, and then verifies that that name is returned
in the player-info event.