Move to using DefaultAzureCredential

Sync.cs

@@ -18,10 +18,6 @@ namespace ASTSync;
 public static class Sync
 {
 
-    private static string _appClientId = Environment.GetEnvironmentVariable("AppClientId", EnvironmentVariableTarget.Process);
-    private static string _appTenantId = Environment.GetEnvironmentVariable("AppTenantId", EnvironmentVariableTarget.Process);
-    private static string _appSecret = Environment.GetEnvironmentVariable("AppSecret", EnvironmentVariableTarget.Process);
-
     // If to pull entra users
     private static bool _pullEntraUsers =
         bool.Parse(Environment.GetEnvironmentVariable("SyncEntra", EnvironmentVariableTarget.Process) ?? "false");
@@ -67,10 +63,7 @@ public static async Task RunAsync([TimerTrigger("0 */15 * * * *")] TimerInfo myT
 
         _log = log;
 
-        // Validate required variables
-        if (string.IsNullOrEmpty(_appClientId) || string.IsNullOrEmpty(_appTenantId) || string.IsNullOrEmpty(_appSecret))
-            throw new Exception("AppClientID, AppTenantID, and AppSecret must be set");
-
+        // Get graph client
         var GraphClient = GetGraphServicesClient();
 
         _log.LogInformation($"C# Timer trigger function executed at: {DateTime.UtcNow}");
@@ -419,18 +412,14 @@ private static async Task GetTenantSimulationUsers(GraphServiceClient GraphClien
     /// <returns></returns>
     private static GraphServiceClient GetGraphServicesClient()
     {
-        // Construct auth provider to Graph
-        var scopes = new[] { "https://graph.microsoft.com/.default" };
-        var tenantId = "common";
+        // Use default azure credential
+        var tokenCredential = new DefaultAzureCredential();
 
-        var options = new TokenCredentialOptions
-        {
-            AuthorityHost = AzureAuthorityHosts.AzurePublicCloud
-        };
+        // Default graph scope
+        var scopes = new[] { "https://graph.microsoft.com/.default" };
 
-        var clientSecretCredential = new ClientSecretCredential(_appTenantId, _appClientId, _appSecret, options);
-
-        return new GraphServiceClient(clientSecretCredential, scopes);
+        // Return graph services client
+        return new GraphServiceClient(tokenCredential, scopes);
     }
 
     /// <summary>