Update AiClientStartupValidationBackgroundService and version

Updated AiClientStartupValidationBackgroundService to use IServiceScopeFactory for creating a new scope, allowing access to IAiClient service inside ExecuteAsync method. A null check is also added for serviceScopeFactory. This change accommodates scenarios where AiClient may be required in the background service. Also, incremented the project version to 4.0.2-alpha in the Directory.Build.props file to reflect latest changes and maintain proper versioning.

src/Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
     <PropertyGroup>
-        <Version>4.0.1-alpha</Version>
+        <Version>4.0.2-alpha</Version>
         <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>

src/OpenAI.ChatGpt.AspNetCore/AiClientStartupValidationBackgroundService.cs

@@ -1,13 +1,20 @@
-using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace OpenAI.ChatGpt.AspNetCore;
 
 internal class AiClientStartupValidationBackgroundService : BackgroundService
 {
+    private readonly IServiceScopeFactory _serviceScopeFactory;
 
-    public AiClientStartupValidationBackgroundService(AiClientFromConfiguration _)
+    public AiClientStartupValidationBackgroundService(IServiceScopeFactory serviceScopeFactory)
     {
+        _serviceScopeFactory = serviceScopeFactory ?? throw new ArgumentNullException(nameof(serviceScopeFactory));
     }
 
-    protected override Task ExecuteAsync(CancellationToken stoppingToken) => Task.CompletedTask;
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        await using var scope = _serviceScopeFactory.CreateAsyncScope();
+        _ = scope.ServiceProvider.GetRequiredService<IAiClient>();
+    }
 }