Add Authority Advisory AI and API Lifecycle Configuration

- Introduced AuthorityAdvisoryAiOptions and related classes for managing advisory AI configurations, including remote inference options and tenant-specific settings.
- Added AuthorityApiLifecycleOptions to control API lifecycle settings, including legacy OAuth endpoint configurations.
- Implemented validation and normalization methods for both advisory AI and API lifecycle options to ensure proper configuration.
- Created AuthorityNotificationsOptions and its related classes for managing notification settings, including ack tokens, webhooks, and escalation options.
- Developed IssuerDirectoryClient and related models for interacting with the issuer directory service, including caching mechanisms and HTTP client configurations.
- Added support for dependency injection through ServiceCollectionExtensions for the Issuer Directory Client.
- Updated project file to include necessary package references for the new Issuer Directory Client library.

src/Authority/StellaOps.Authority/StellaOps.Auth.Client/ServiceCollectionExtensions.cs

@@ -68,6 +68,29 @@ public static class ServiceCollectionExtensions
         return services;
     }
 
+    /// <summary>
+    /// Adds authentication and tenancy header handling for an <see cref="HttpClient"/> registered via <see cref="IHttpClientBuilder"/>.
+    /// </summary>
+    public static IHttpClientBuilder AddStellaOpsApiAuthentication(this IHttpClientBuilder builder, Action<StellaOpsApiAuthenticationOptions> configure)
+    {
+        ArgumentNullException.ThrowIfNull(builder);
+        ArgumentNullException.ThrowIfNull(configure);
+
+        builder.Services.AddOptions<StellaOpsApiAuthenticationOptions>(builder.Name)
+            .Configure(configure)
+            .PostConfigure(static options => options.Validate());
+
+        builder.AddHttpMessageHandler(provider => new StellaOpsBearerTokenHandler(
+            builder.Name,
+            provider.GetRequiredService<IOptionsMonitor<StellaOpsApiAuthenticationOptions>>(),
+            provider.GetRequiredService<IOptionsMonitor<StellaOpsAuthClientOptions>>(),
+            provider.GetRequiredService<IStellaOpsTokenClient>(),
+            provider.GetService<TimeProvider>(),
+            provider.GetService<ILogger<StellaOpsBearerTokenHandler>>()));
+
+        return builder;
+    }
+
     private static IAsyncPolicy<HttpResponseMessage> CreateRetryPolicy(IServiceProvider provider)
     {
         var options = provider.GetRequiredService<IOptionsMonitor<StellaOpsAuthClientOptions>>().CurrentValue;