Add MediatR, FluentValidation, AutoMapper, and EF Core

Updated application and infrastructure layers to include MediatR, FluentValidation, AutoMapper, and Entity Framework Core.

- Added new dependencies to `DigitalData.TaskFlow.Application.csproj` and `DigitalData.TaskFlow.Infrastructure.csproj` for MediatR, FluentValidation, AutoMapper, and EF Core.
- Configured MediatR with options and license key support.
- Registered validators and AutoMapper profiles in the application layer.
- Introduced `MediatROptions` and `SwaggerOptions` for configuration.
- Updated `appsettings.json` with connection strings and configuration sections for MediatR and Swagger.
- Replaced placeholder comments in `DependencyInjection` classes with actual service registrations.
- Upgraded `Swashbuckle.AspNetCore` and added `FluentValidation.AspNetCore` for API validation.

src/core/DigitalData.TaskFlow.Application/DependencyInjection.cs

@@ -1,5 +1,9 @@
-using Microsoft.Extensions.Configuration;
+using DigitalData.TaskFlow.Application.Options;
+using FluentValidation;
+using MediatR;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using System.Reflection;
 
 namespace DigitalData.TaskFlow.Application;
 
@@ -7,8 +11,27 @@ public static class DependencyInjection
 {
     public static IServiceCollection AddApplicationServices(this IServiceCollection services, IConfiguration configuration)
     {
-        // Register application services here
-        // Example: services.AddSingleton<IMyService, MyService>();
+        var mediatROptions = configuration
+            .GetSection(MediatROptions.SectionName)
+            .Get<MediatROptions>();
+
+        services
+            .AddOptions<MediatROptions>()
+            .Bind(configuration.GetSection(MediatROptions.SectionName));
+
+        services.AddMediatR(config =>
+        {
+            config.RegisterServicesFromAssembly(typeof(DependencyInjection).Assembly);
+
+            if (!string.IsNullOrWhiteSpace(mediatROptions?.LuckyPennySoftLicenseKey))
+            {
+                config.LicenseKey = mediatROptions.LuckyPennySoftLicenseKey;
+            }
+        });
+
+        services.AddValidatorsFromAssembly(typeof(DependencyInjection).Assembly);
+        services.AddAutoMapper(_ => { }, Assembly.GetExecutingAssembly());
+
         return services;
     }
 }