Add integration test project with MediatR procedure tests

Added ReC.Tests project with integration tests for stored procedure commands and queries via MediatR, covering endpoints, actions, results, and profiles. Introduced a test base for DI/configuration, helper for private property access, and updated the solution to include the new test suite. Tests use NUnit and cover both positive and negative scenarios.

tests/ReC.Tests/Application/RecApplicationTestBase.cs

@@ -0,0 +1,73 @@
+using System;
+using System.IO;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using ReC.Application;
+using ReC.Application.Common.Options;
+using ReC.Infrastructure;
+
+namespace ReC.Tests.Application;
+
+public abstract class RecApplicationTestBase : IDisposable
+{
+    protected RecApplicationTestBase()
+    {
+        Configuration = BuildConfiguration();
+        ServiceProvider = BuildServiceProvider(Configuration);
+    }
+
+    protected IConfiguration Configuration { get; }
+
+    protected IServiceProvider ServiceProvider { get; }
+
+    private static IConfiguration BuildConfiguration()
+    {
+        var appSettingsPath = LocateApiAppSettings();
+
+        return new ConfigurationBuilder()
+            .AddJsonFile(appSettingsPath, optional: false, reloadOnChange: false)
+            .Build();
+    }
+
+    private static IServiceProvider BuildServiceProvider(IConfiguration configuration)
+    {
+        var services = new ServiceCollection();
+
+        services.AddSingleton(configuration);
+
+        services.AddRecServices(options =>
+        {
+            options.LuckyPennySoftwareLicenseKey = configuration["LuckyPennySoftwareLicenseKey"];
+            options.ConfigureRecActions(configuration.GetSection("RecAction"));
+        });
+
+        services.AddRecInfrastructure(opt =>
+        {
+            opt.ConfigureDbContext((_, builder) => builder.UseSqlServer(configuration.GetConnectionString("Default")));
+        });
+
+        return services.BuildServiceProvider();
+    }
+
+    private static string LocateApiAppSettings()
+    {
+        var current = new DirectoryInfo(AppContext.BaseDirectory);
+        while (current is not null)
+        {
+            var candidate = Path.Combine(current.FullName, "src", "ReC.API", "appsettings.json");
+            if (File.Exists(candidate))
+                return candidate;
+
+            current = current.Parent;
+        }
+
+        throw new FileNotFoundException("Could not locate src/ReC.API/appsettings.json from test base directory.");
+    }
+
+    public void Dispose()
+    {
+        if (ServiceProvider is IDisposable disposable)
+            disposable.Dispose();
+    }
+}