Termine im Outlook Gruppenkalender erstellen mit PHP

Calendars.Read
Calendars.Read.Shared
Calendars.ReadBasic
Calendars.ReadBasic.All
Calendars.ReadWrite
Calendars.ReadWrite.Shared
Group.Create
Group.Read.All
Group.Read.All
Group.ReadWrite.All
GroupMember.Read.All
GroupMember.ReadWrite.All
User.Read
User.Read.All

<?php
$url = 'https://login.microsoftonline.com/{tennant-ID}/oauth2/v2.0/token';  
$data = [
    'client_id' => '***',  
    'scope' => 'https://graph.microsoft.com/.default',  
    'client_secret' => '***',  
    'grant_type' => 'client_credentials'  
];

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Content-type: application/x-www-form-urlencoded'  
]);

$result = curl_exec($ch);
if ($result === false) {
    echo 'Curl-Fehler: ' . curl_error($ch);  
}

curl_close($ch);
$response = json_decode($result, true);

if (isset($response['access_token'])) {  
    $token = $response['access_token'];  
} else {
    echo "Access Token nicht in der Antwort gefunden!";  
    die();
}
$token = $response['access_token'];   


//Hiermit kann ich einen Termin in meinem Kalender erstellen
//$userId = '***';  
//$url = "https://graph.microsoft.com/v1.0/users/$userId/events"; 


//Hiermit möchte ich einen Termin im Gruppenkalender erstellen
//$groupId = '***';  
$url = 'https://graph.microsoft.com/v1.0/groups/$groupId/events';  
//$url = 'https://graph.microsoft.com/v1.0/groups/$groupId/calendar/events'; 


$eventData = [
    'subject' => 'Automatisierter Testtermin',  
    'start' => [  
        'dateTime' => '2023-08-17T12:00:00',  
        'timeZone' => 'UTC'  
    ],
    'end' => [  
        'dateTime' => '2023-08-17T13:00:00',  
        'timeZone' => 'UTC'  
    ],
    'body' => [  
        'contentType' => 'HTML',  
        'content' => 'Kann gelöscht werden. .'  
    ]
];

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_VERBOSE, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($eventData));
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Authorization: Bearer $token",  
    "Content-Type: application/json"  
]);

$result = curl_exec($ch);
if (curl_errno($ch)) {
    echo 'Curl error: ' . curl_error($ch);  
}

$response = json_decode($result, true);
curl_close($ch);

if (isset($response['id'])) {  
    echo "Termin erfolgreich erstellt mit ID: " . $response['id'];  
} else {
    echo "Fehler beim Erstellen des Termins.";  
}
if (isset($response['error'])) {  
    echo "Fehler: " . $response['error']['message'];  
}

array(2) { ["code"]=> string(17) "ErrorAccessDenied" ["message"]=> string(50) "Access is denied. Check credentials and try again." } }