Restruture application layer.

PSManagement.Application/Abstraction/Messaging/ICommand.cs

+using MediatR;
+
+namespace PSManagement.Application.Abstraction.Messaging
+{
+    public interface ICommand<out TResponse> : IRequest<TResponse>
+    {
+    }
+}

PSManagement.Application/Abstraction/Messaging/ICommandHandler.cs

+using MediatR;
+
+namespace PSManagement.Application.Abstraction.Messaging
+{
+    public interface ICommandHandler<in TCommand, TResponse> : IRequestHandler<TCommand, TResponse>
+                         where TCommand : ICommand<TResponse>
+    {
+    }
+}

PSManagement.Application/Abstraction/Messaging/IQuery.cs

+using MediatR;
+
+namespace PSManagement.Application.Abstraction.Messaging
+{
+    public interface IQuery<out TResponse> : IRequest<TResponse>
+    {
+    }
+}

PSManagement.Application/Abstraction/Messaging/IQueryHandler.cs

+using MediatR;
+
+namespace PSManagement.Application.Abstraction.Messaging
+{
+    public interface IQueryHandler<in TQuery, TResponse> : IRequestHandler<TQuery, TResponse>
+    where TQuery : IQuery<TResponse>
+    {
+    }
+}

PSManagement.Application/Behaviors/ValidationBehavior/ValidationBehavior.cs

+using MediatR;
+using PSManagement.Application.Abstraction.Messaging;
+using PSManagement.Application.Common.Exceptions;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using ValidationException = PSManagement.Application.Common.Exceptions.ValidationException;
+
+namespace PSManagement.Application.Behaviors.ValidationBehavior
+{
+    public sealed class ValidationBehavior<TRequest, TResponse> //: IPipelineBehavior<TRequest, TResponse>
+//     where TRequest : class, ICommand<TResponse>
+    {
+        //private readonly IEnumerable<IValidator<TRequest>> _validators;
+
+        //public ValidationBehavior(IEnumerable<IValidator<TRequest>> validators) => _validators = validators;
+
+        //public async Task<TResponse> Handle(
+        //    TRequest request,
+        //    CancellationToken cancellationToken,
+        //    RequestHandlerDelegate<TResponse> next)
+        //{
+        //    if (!_validators.Any())
+        //    {
+        //        return await next();
+        //    }
+
+        //    var context = new ValidationContext<TRequest>(request);
+
+        //    var errorsDictionary = _validators
+        //        .Select(x => x.Validate(context))
+        //        .SelectMany(x => x.Errors)
+        //        .Where(x => x != null)
+        //        .GroupBy(
+        //            x => x.PropertyName,
+        //            x => x.ErrorMessage,
+        //            (propertyName, errorMessages) => new
+        //            {
+        //                Key = propertyName,
+        //                Values = errorMessages.Distinct().ToArray()
+        //            })
+        //        .ToDictionary(x => x.Key, x => x.Values);
+
+        //    if (errorsDictionary.Any())
+        //    {
+        //        throw new ValidationException(errorsDictionary);
+        //    }
+
+        //    return await next();
+        //}
+    }
+}

PSManagement.Application/Class1.cs

-using System;
-
-namespace PSManagement.Application
-{
-    public class Class1
-    {
-    }
-}

PSManagement.Application/Common/Exceptions/ValidtaitonException.cs

+using PSManagement.SharedKernel.DomainException;
+using System.Collections.Generic;
+
+namespace PSManagement.Application.Common.Exceptions
+{
+    public sealed class ValidationException : BadRequestException
+    {
+        public ValidationException(Dictionary<string, string[]> errors)
+            : base("Validation errors occurred") =>
+            Errors = errors;
+
+        public Dictionary<string, string[]> Errors { get; }
+    }
+}

PSManagement.Application/Common/Providers/IDateTimeProvider.cs

+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace PSManagement.Application.Common.Services
+{
+    public interface IDateTimeProvider
+    {
+        public DateTime UtcNow { get; }
+    }
+}

PSManagement.Application/Contracts/Authentication/AuthenticationResult.cs

+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace PSManagement.Application.Contracts.Authentication
+{
+    public class AuthenticationResult
+    {
+        public Guid Id { get; set; }
+        public String Email { get; set; }
+        public String LastName { get; set; }
+        public String FirstName { get; set; }
+        public String Token { get; set; }
+
+    }
+}

PSManagement.Application/Contracts/Authentication/IAuthenticationService.cs

+using System;
+using System.Threading.Tasks;
+
+namespace PSManagement.Application.Contracts.Authentication
+{
+    public interface IAuthenticationService
+    {
+        public Task<AuthenticationResult> Login(String email , String password);
+        public Task<AuthenticationResult> Register(String email,String firstName ,String lastName, String password);
+
+
+    }
+
+}

PSManagement.Application/Contracts/Authentication/IJwtTokenGenerator.cs

+using System;
+
+namespace PSManagement.Application.Contracts.Authentication
+{
+    public interface IJwtTokenGenerator
+    {
+        public String GenerateToken(Guid id , String firstName , String lastName,String email );
+    }
+}

PSManagement.Application/DI/DependencyInjection.cs

 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using PSManagement.Application.Contracts.Authentication;
 
 namespace PSManagement.Application.DI
 {

PSManagement.Application/PSManagement.Application.csproj

-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <Folder Include="Common\" />
     <Folder Include="Services\" />
     <Folder Include="UseCases\" />
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="MediatR" Version="5.1.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="5.0.0" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="5.0.2" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\PSManagement.SharedKernel\PSManagement.SharedKernel.csproj" />
+  </ItemGroup>
+
 </Project>