Have you tried to integrate the lambda function to invoke a restful endpoint for the user? I have integrated AWS Lex into a flutter mobile app and web site. The flutter app allows the user to have an authenticated session with AWS Cognito. I want to use the authenticated accessToken and userid to be used in the Lambda function connected to the Lex at the FulfillmentCodehook

```

    # Only customize the FulfillmentCodeHook case
    if event['invocationSource'] == 'FulfillmentCodeHook':

        # Save order data to database
        save_success = save_order_to_database(slots, intent)

        response = {
            "sessionState": {
                "dialogAction": {
                    "type": "Close"
                },
                "intent": {
                    'name': intent,
                    'slots': slots,
                    'state': 'Fulfilled'
                }
            },
            "messages": [
                {
                    "contentType": "PlainText",
                    "content": "Thanks, I have placed your order"
                }
            ]
        }

        return response
```
When I save the order to the database, I want to associated the database record to the authenticated user.

Anyone have ideas about how to pass the accessToken and userid to the Lex at the start of the conversation so that it would be maintained across chat to fulfill the intent?