title: Powershell - List subscriptions of a specific management group
body: <p>On Azure and with Powershell, I need to list all the subscriptions that are in a specific management group.
  The command Get-AzSubscription has no parameter to filter on a specific management group. And there is no powershell command (AzManagementGroup) either to list the subscriptions inside.</p>
  <p>I was thinking about creating an msgraph query to do that and call it from powershell, but perhaps there is an easier way to do that? :)</p>