refactor(ServiceRegistrator): enhance handler resolution logic and improve readability

- Removed unnecessary using directive for Notification.
- Refactored the handler resolution logic to use pattern matching for better clarity and performance.
- Updated the handling of single handler scenarios to utilize IReadOnlyList for improved type safety and readability.
- These changes streamline the service registration process and enhance maintainability without altering existing functionality.

Author: aminafra

src/DispatchR/Configuration/ServiceRegistrator.cs

@@ -1,5 +1,4 @@
-using DispatchR.Abstractions.Notification;
-using DispatchR.Abstractions.Send;
+using DispatchR.Abstractions.Send;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace DispatchR.Configuration
@@ -142,20 +141,23 @@ public static void RegisterHandlers(IServiceCollection services, List<Type> allT
                         }
                     }
 
-                services.AddScoped(handlerInterface, sp =>
-                {
-                    var keyedServices = sp.GetKeyedServices<IRequestHandler>(key);
+                    services.AddScoped(handlerInterface, sp =>
+                    {
+                        var keyedServices = sp.GetKeyedServices<IRequestHandler>(key);
 
-                    var pipelinesWithHandler = keyedServices as IRequestHandler[] ?? keyedServices.ToArray();
+                        IReadOnlyList<IRequestHandler> pipelinesWithHandler = keyedServices switch
+                        {
+                            IRequestHandler[] asArray => asArray,
+                            IReadOnlyList<IRequestHandler> asList => asList,
+                            _ => keyedServices.ToArray()
+                        };
 
-                    // Single handler - no pipeline chaining needed
-                    if (pipelinesWithHandler.Length == 1)
-                    {
-                        return pipelinesWithHandler[0];
-                    }
+                        // Single handler - no pipeline chaining needed
+                        if (pipelinesWithHandler.Count == 1)
+                            return pipelinesWithHandler[0];
 
                         IRequestHandler lastPipeline = pipelinesWithHandler[0];
-                        for (int i = 1; i < pipelinesWithHandler.Length; i++)
+                        for (var i = 1; i < pipelinesWithHandler.Count; i++)
                         {
                             var pipeline = pipelinesWithHandler[i];
                             pipeline.SetNext(lastPipeline);