rewrite websocket code to avoid deprecated pekko-http code (and switch to the maintained code)

UpgradeToWebSocket is deprecated (for years) and will be removed in pekko-http 2.0.0
The supported websocket code in pekko-http is based on request.attribute(AttributeKeys.websocketUpgrade) and this returns a WebSocketUpgrade instance
The handleMessages on WebSocketUpgrade expects a Flow that works with pekko-http ws.Message classes. These ws.Message definitions are similar to the Play WebSocket Message instances.
We probably need to convert the Play Flow that works with Play Messages to a Flow that works with pekko-http ws.Message instances so that we can use WebSocketUpgrade.handleMessages.

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