Enhance framework compatibility and code readability

Added preprocessor directives for .NET framework compatibility.
Modified `using` directives to be framework-specific.
Improved code formatting for better readability.
Introduced obsolete attributes for deprecated methods,
recommending `MediatR` as an alternative.
Added XML documentation for clarity and maintainability.

DigitalData.Core.Abstraction.Application/Repository/IEntityMapper.cs

@@ -1,4 +1,7 @@
-namespace DigitalData.Core.Abstraction.Application.Repository
+#if NETFRAMEWORK
+using System.Collections.Generic;
+#endif
+namespace DigitalData.Core.Abstraction.Application.Repository
 {
     /// <summary>
     /// Defines methods for mapping between entities and Data Transfer Objects (DTOs).