I have a Microsoft Teams Tab application (App1) that displays another web application (App2) using an iframe. App2 is registered under a different tenant than App1. I need to access the Microsoft Graph API in App2 to list user groups (/me/memberOf). This API requires delegated permissions Group.Read.All and GroupMember.Read.All. Since popup windows are blocked in the Teams desktop client, I cannot acquire an access token for the Graph API inside App2.