client-credentials-for-aad.ps1

$clientId = '<client-id>'
$clientSecret = '<client-secret>'
$tenantId = "<your-tenant-id>"
$scope = 'https://graph.microsoft.com/.default'
$tokenEndpoint = "https://login.microsoftonline.com/$tenantId/oauth2/v2.0/token"
$postParams = @{
    client_id = $clientId;
    client_secret = $clientSecret;
    grant_type = 'client_credentials';
    scope = $scope
}

$authResult = (Invoke-WebRequest -Uri $tokenEndpoint -Method POST -ContentType "application/x-www-form-urlencoded" -Body $postParams) | ConvertFrom-Json