[Access] Implement keepalive routine with ping-ponging to ws connection in ws controller

[Guitarheroua]

Develop a separate Keepalive module for the web socket controller to monitor network availability using WebSocket ping-pong service messages.

Requirements:

• The Keepalive module should be instantiated and managed by the web socket controller but function independently.
• The module should operate autonomously to detect connectivity issues.
• If issues are detected, it should:
  • Disable the WebSocket connection.
  • Trigger a graceful shutdown of the affected parts of the web socket controller.
• The logic for this functionality can be derived from the proof of concept (PoC) implementation in Flow-Go:
  

  flow-go/engine/access/rest/routes/websocket_broker.go

  Lines 264 to 277 in 173f141

  	// sendPing sends a periodic ping message to the WebSocket client to keep the connection alive.
  	func (w *WebSocketBroker) sendPing() error {
  	if err := w.conn.SetWriteDeadline(time.Now().Add(writeWait)); err != nil {
  	w.handleWSError(models.NewRestError(http.StatusInternalServerError, "failed to set the initial write deadline for ping", err))
  	return err
  	}
  	if err := w.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
  	w.handleWSError(err)
  	return err
  	}
  	return nil
  	}

• Provide tests to validate proper detection and handling of connectivity issues.

[Guitarheroua]

@UlyanaAndrukhiv Also, check a chapter for gorilla control messages documentation, to be sure, that ping-pong handles correctly.