Deeplink to Teams-tab with stageview

Hi All,

I'm trying to create an simpel button/app in the vertical menu of Teams.

If the user clicks on the button, they have to be navigated to a channel tab in Teams.
This works fine for the normal view: with channels visible in the left pane.
I'm trying to get the deeplink to redirect to Stageview immediatly. And I can't seem to get it to work.

I tried everything I could with the documentation on docs.microsoft on Unfurling and stageview, but no luck.
What I have made so far:

1. Created a subsite in SharePoint.
2. Created a new .aspx with the "execute deeplink" script
3. Set the new .aspx as homepage on the subsite

4. created a simple app with app studio with a link to the subsite.

This all works fine for "normal" tabview, but not for stageview.

What should i Insert in this syntax?
https://teams.microsoft.com/l/stage/{appId}/0?context={"contentUrl":"contentUrl","websiteUrl":"websiteUrl","name":"Contoso"}
{appId} = The id of the app in the Teams App Center, i created with app studio?
ContentUrl = The link to the tab?
WebsiteUrl = Link to the tab?
name = optional?

Thanks in advance for your replies!