Single Sign On from Website to embedded Bot Framework Webchat component

Question

This should be a common use case, but I can't find a thorough explanation on how to achieve this. I have a MVC C# Web Application, and a Bot built with Bot Composer. I have both in Azure Web Apps, and the Bot has a registration for the Directline channel. I would like to have the website, which uses AD authentication, to be able to pass the token when the bot shows the OAuth login card.

https://learn.microsoft.com/en-us/azure/bot-service/bot-builder-concept-sso?view=azure-bot-service-4.0#sso-components-interaction

Basically I want to do what is described in the image for the WebChat control.

Any help is greatly appreciated

I tried this:

window.WebChat.renderWebChat({
        directLine: window.WebChat.createDirectLine({ token: '@ViewData["DirectLineToken"]' }),
        username: 'Web Chat User',
        locale: 'en-US',
        botAvatarInitials: 'WC',
        userAvatarInitials: 'WW'
    }, document.getElementById('webchat'));

the bot is rendered correctly, and the signin card is shown.

I suspect that there should be a configuration in the "Token Exchange Url" box, or some place where the website acquired token should be placed to be read by the bot, but I have no clue where to go from here.