Core overall function: Listen to messages from Faye about changes to the queue or people being called. When getting a message, normalize the incoming message data, and update the display based on the new data.
If several people are called at once, things get tricky so that we can allow each student some time displayed on the calling screen.
The calling aviodence logic is here: https://github.umn.edu/asrweb/queue_signage/blob/9659a7fd5d96c53b2c34d4673a66e9c082c83c69/app/routes/visitors.js#L56