Add events aggregator

Hcs.WebApp/BackgroundServices/OperationExecutionState.cs

@@ -5,10 +5,6 @@ namespace Hcs.WebApp.BackgroundServices
 {
     public class OperationExecutionState
     {
-        public delegate void OperationStarted(int operationId, int campaignId, DateTime startedAt);
-        public delegate void OperationExecuted(int operationId, int campaignId, string messageGuid);
-        public delegate void OperationEnded(int operationId, int campaignId, DateTime endedAt, string failureReason);
-
         private readonly ConcurrentQueue<Operation> operationsInQueue = new();
         private readonly HashSet<Operation> operationsInProcess = [];