Add Graph API client integration to entra class

Introduce methods to initialize a GraphServiceClient and ClientCredentialContext, leveraging configuration values for authentication. This enables interaction with Microsoft Graph API in a structured and secure manner.

services/nginx/app/classes/entra.php

@@ -5,6 +5,8 @@ namespace classes;
 require_once WD . '/modules/entra/entra_c.php';
 
 use entra\entra_c;
+use Microsoft\Graph\GraphServiceClient;
+use Microsoft\Kiota\Authentication\Oauth\ClientCredentialContext;
 
 class entra
 {
@@ -18,4 +20,18 @@ class entra
     {
         $this->config = new entra_c();
     }
+
+    public function getGraphClient(): GraphServiceClient
+    {
+        return new GraphServiceClient($this->getTokenRequestContext());
+    }
+
+    public function getTokenRequestContext(): ClientCredentialContext
+    {
+        return new ClientCredentialContext(
+            $this->config->tenant_id->getVariableValue(),
+            $this->config->client_id->getVariableValue(),
+            $this->config->client_secret->getVariableValue()
+        );
+    }
 }