Refactor session ID check to handle large batches

Refactored `CheckIfSessionsAlreadyExists` to process session IDs in batches of 20, improving performance and avoiding query size limitations. The new implementation splits session IDs, constructs and executes queries for each batch, and combines results into a single list of unique existing session IDs.

BeyondTrustConnector/AccessSessionUpdater.cs

@@ -104,10 +104,23 @@ public async Task Run([TimerTrigger("0 */15 * * * *", RunOnStartup = false)] Tim
 
     private static async Task<List<string?>> CheckIfSessionsAlreadyExists(QueryService queryService, IEnumerable<XElement> sessions)
     {
-        var sessionIds = sessions.Select(s => s.Attribute("lsid")!.Value).Distinct().Aggregate(string.Empty, (current, next) => current += $"'{next}',").TrimEnd(',');
-        var existingSessionResult = await queryService.QueryWorkspace($"BeyondTrustAccessSession_CL | where SessionId in ({sessionIds}) | project SessionId");
-        var existingSessions = existingSessionResult?.Table.Rows.Select(r => r[0].ToString()).ToList() ?? [];
-        return existingSessions;
+        var sessionIds = sessions.Select(s => s.Attribute("lsid")!.Value).Distinct().ToList();
+        var existingSessions = new List<string?>();
+
+        const int batchSize = 20;
+        for (int i = 0; i < sessionIds.Count; i += batchSize)
+        {
+            var batch = sessionIds.Skip(i).Take(batchSize);
+            var batchIds = string.Join(",", batch.Select(id => $"'{id}'"));
+            var query = $"BeyondTrustAccessSession_CL | where SessionId in ({batchIds}) | project SessionId";
+            var existingSessionResult = await queryService.QueryWorkspace(query);
+            if (existingSessionResult?.Table.Rows is not null)
+            {
+                existingSessions.AddRange(existingSessionResult.Table.Rows.Select(r => r[0].ToString()));
+            }
+        }
+
+        return existingSessions.Distinct().ToList();
     }
 
     private static List<Dictionary<string, object>> GetUserDetails(XElement session, string ns)