Refactor: migrate to open-source MediatR-compatible core

Replaced original mediator interfaces and implementation with a forked, open-source MediatR (pre-commercial) core. Updated namespaces, interfaces, and behaviors to match MediatR's extensibility model. Added DI registration, notification publisher strategies, handler ordering, and pipeline support. Updated project metadata and license to Apache-2.0. Removed legacy EasyMediator code. This makes the library a drop-in, open-source MediatR-compatible alternative.

Author: Vadim Belov

Sources/EasyExtensions.Mediator/Contracts/IBaseRequest.cs

@@ -1,13 +1,7 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2025–2026 Vadim Belov <https://belov.us>
-
 namespace EasyExtensions.Mediator.Contracts
 {
     /// <summary>
-    /// Defines a marker interface for notification messages used in a messaging or event-driven system.
+    /// Marker interface to represent a notification
     /// </summary>
-    /// <remarks>Implement this interface to represent a notification that can be published or handled by
-    /// notification handlers. This interface does not define any members and serves to identify types as notifications
-    /// within the system.</remarks>
     public interface INotification { }
-}
+}

Sources/EasyExtensions.Mediator/Contracts/IMediator.cs

@@ -1,20 +1,18 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2025–2026 Vadim Belov <https://belov.us>
-
 namespace EasyExtensions.Mediator.Contracts
 {
     /// <summary>
-    /// Represents a request message in the API infrastructure.
+    /// Marker interface to represent a request with a void response
     /// </summary>
-    /// <remarks>This interface serves as a marker for request types that are processed by the API pipeline.
-    /// Implementing this interface allows a type to be recognized as a request and handled accordingly by request handlers
-    /// or middleware components. It extends the <see cref="IBaseRequest"/> interface to provide additional context or
-    /// categorization for request objects.</remarks>
     public interface IRequest : IBaseRequest { }
 
     /// <summary>
-    /// Defines a request that returns a response of the specified type when handled.
+    /// Marker interface to represent a request with a response
     /// </summary>
-    /// <typeparam name="TResponse">The type of the response returned by the request.</typeparam>
+    /// <typeparam name="TResponse">Response type</typeparam>
     public interface IRequest<out TResponse> : IBaseRequest { }
+
+    /// <summary>
+    /// Allows for generic type constraints of objects implementing IRequest or IRequest{TResponse}
+    /// </summary>
+    public interface IBaseRequest { }
 }