Outlook Feiertage automatisch hinterlegen und als abwesend buchen

# Variablen
$clientId = "YOUR_CLIENT_ID"  
$clientSecret = "YOUR_CLIENT_SECRET"  
$tenantId = "YOUR_TENANT_ID"  
# ---------------------------------------
$redirectUri = "http://localhost"  
$resource = "https://graph.microsoft.com"  
$authority = "https://login.microsoftonline.com/$tenantId"  
$scope = "https://graph.microsoft.com/.default"  

$tokenBody = @{
    client_id     = $clientId
    scope         = $scope
    client_secret = $clientSecret
    grant_type    = 'client_credentials'  
}

$accessToken = (Invoke-RestMethod -Method Post -Uri "$authority/oauth2/v2.0/token" -Body $tokenBody).access_token  

function UpdateHolidayEvents($userId) {
    foreach ($event in Invoke-RestMethod -Uri "$resource/v1.0/users/$userId/calendar/events" -Headers @{Authorization = "Bearer $accessToken"} | Select-Object -ExpandProperty value) {  
        if ($event.categories -contains "Feiertag" -and $event.showAs -ne "OOF" -and $event.isAllDay -eq $true -and $event.isCancelled -eq $false) {  
            Invoke-RestMethod -Method Patch -Uri "$resource/v1.0/users/$userId/calendar/events/$($event.id)" -Headers @{Authorization = "Bearer $accessToken"} -ContentType "application/json" -Body (@{showAs = "OOF"} | ConvertTo-Json -Depth 4)  
            Write-Host "Holiday event updated for user: $userId"  
        }
    }
}

foreach ($user in Invoke-RestMethod -Uri "$resource/v1.0/users" -Headers @{Authorization = "Bearer $accessToken"} | Select-Object -ExpandProperty value) {  
    UpdateHolidayEvents($user.id)
}