refactor(di): add AddApplication entry point and generic AddValidatedOptions

- Add Musify.Application.AddApplication(services, config) as the layer's DI
  entry point: registers Mediator, UploadIntentValidator and all app configs
- Collapse the 5 near-identical AddXConfiguration methods into a single
  generic AddValidatedOptions<T>(config, section)
- Move UploadIntentValidator registration out of Infrastructure into the
  Application layer (fixes layering leak); Infra config binding now uses the
  generic helper
- Api calls AddApplication; Worker uses AddValidatedOptions for its configs

Build: 0 warnings, 0 errors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/Musify.Api/Extensions/ServiceCollectionExtensions.cs

@@ -1,7 +1,7 @@
 using FluentValidation;
 using Musify.Infrastructure.MassTransit;
 using Musify.Infrastructure.Persistence;
-using Musify.Application.Configuration;
+using Musify.Application;
 using Musify.Infrastructure.Services;
 using Musify.Api.Authentication;
 using Musify.Api.DataTransferObjects.PlayLists;
@@ -14,16 +14,11 @@ public static class ServiceCollectionExtensions
 {
     public static IServiceCollection AddApplicationServices(this IServiceCollection services, IConfiguration configuration)
     {
+        services.AddApplication(configuration);
         services.AddDatabase(configuration);
-        services.AddApplicationStorageConfiguration(configuration);
-        services.AddPlayListConfiguration(configuration);
-        services.AddTrackConfiguration(configuration);
-        services.AddStreamGatewayConfiguration(configuration);
         services.AddStorageService(configuration);
         services.AddStreamTicketService(configuration);
-        services.AddUploadIntentConfiguration(configuration);
         services.AddMassTransitClient(configuration);
-        services.AddMediator();
         services.AddAuthenticationConfiguration(configuration);
         services.AddOpenApiConfiguration();
         services.AddScalarConfiguration();

backend/Musify.Application/ApplicationDependencyInjection.cs

@@ -0,0 +1,24 @@
+using Mediator;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Musify.Application.Configuration;
+using Musify.Application.Services;
+
+namespace Musify.Application;
+
+public static class ApplicationDependencyInjection
+{
+    public static IServiceCollection AddApplication(this IServiceCollection services, IConfiguration configuration)
+    {
+        services.AddMediator();
+        services.AddScoped<UploadIntentValidator>();
+
+        services.AddValidatedOptions<ApplicationStorageConfiguration>(configuration, ApplicationStorageConfiguration.SectionName);
+        services.AddValidatedOptions<PlayListConfiguration>(configuration, PlayListConfiguration.SectionName);
+        services.AddValidatedOptions<TrackConfiguration>(configuration, TrackConfiguration.SectionName);
+        services.AddValidatedOptions<StreamGatewayConfiguration>(configuration, StreamGatewayConfiguration.SectionName);
+        services.AddValidatedOptions<UploadIntentConfiguration>(configuration, UploadIntentConfiguration.SectionName);
+
+        return services;
+    }
+}

backend/Musify.Application/Configuration/ConfigurationDependencyInjection.cs

@@ -1,57 +1,25 @@
-using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 
-namespace Musify.Application.Configuration
+namespace Musify.Application.Configuration;
+
+public static class ConfigurationDependencyInjection
 {
-    public static class ConfigurationDependencyInjection
+    public static IServiceCollection AddValidatedOptions<T>(
+        this IServiceCollection services,
+        IConfiguration configuration,
+        string sectionName)
+        where T : class
     {
-        public static IServiceCollection AddApplicationStorageConfiguration(this IServiceCollection serviceDescriptors, IConfiguration configuration)
+        services
-        {
+            .AddOptionsWithValidateOnStart<T>()
-            serviceDescriptors
+            .Bind(configuration.GetRequiredSection(sectionName))
-                .AddOptionsWithValidateOnStart<ApplicationStorageConfiguration>()
+            .ValidateDataAnnotations();
-                .Bind(configuration.GetRequiredSection(ApplicationStorageConfiguration.SectionName))
-                .ValidateDataAnnotations();
-            serviceDescriptors.AddSingleton(serviceProvider =>
-                serviceProvider.GetRequiredService<IOptions<ApplicationStorageConfiguration>>().Value);
 
-            return serviceDescriptors;
+        services.AddSingleton(serviceProvider =>
-        }
+            serviceProvider.GetRequiredService<IOptions<T>>().Value);
 
-        public static IServiceCollection AddPlayListConfiguration(this IServiceCollection serviceDescriptors, IConfiguration configuration)
+        return services;
-        {
-            serviceDescriptors
-                .AddOptionsWithValidateOnStart<PlayListConfiguration>()
-                .Bind(configuration.GetRequiredSection(PlayListConfiguration.SectionName))
-                .ValidateDataAnnotations();
-            serviceDescriptors.AddSingleton(serviceProvider =>
-                serviceProvider.GetRequiredService<IOptions<PlayListConfiguration>>().Value);
-
-            return serviceDescriptors;
-        }
-
-        public static IServiceCollection AddTrackConfiguration(this IServiceCollection serviceDescriptors, IConfiguration configuration)
-        {
-            serviceDescriptors
-                .AddOptionsWithValidateOnStart<TrackConfiguration>()
-                .Bind(configuration.GetRequiredSection(TrackConfiguration.SectionName))
-                .ValidateDataAnnotations();
-            serviceDescriptors.AddSingleton(serviceProvider =>
-                serviceProvider.GetRequiredService<IOptions<TrackConfiguration>>().Value);
-
-            return serviceDescriptors;
-        }
-
-        public static IServiceCollection AddStreamGatewayConfiguration(this IServiceCollection serviceDescriptors, IConfiguration configuration)
-        {
-            serviceDescriptors
-                .AddOptionsWithValidateOnStart<StreamGatewayConfiguration>()
-                .Bind(configuration.GetRequiredSection(StreamGatewayConfiguration.SectionName))
-                .ValidateDataAnnotations();
-            serviceDescriptors.AddSingleton(serviceProvider =>
-                serviceProvider.GetRequiredService<IOptions<StreamGatewayConfiguration>>().Value);
-
-            return serviceDescriptors;
-        }
     }
-}
+}

backend/Musify.Infrastructure/Services/ServicesDependencyInjection.cs

@@ -5,7 +5,6 @@ using Microsoft.Extensions.Options;
 using Musify.Application.Configuration;
 using Musify.Infrastructure.Configuration;
 using Musify.Infrastructure.Jobs;
-using Musify.Application.Services;
 using Musify.Application.Contracts;
 
 namespace Musify.Infrastructure.Services
@@ -46,15 +45,7 @@ namespace Musify.Infrastructure.Services
 
         public static IServiceCollection AddUploadIntentConfiguration(this IServiceCollection serviceDescriptors, IConfiguration configuration)
         {
-            serviceDescriptors
+            serviceDescriptors.AddValidatedOptions<UploadIntentConfiguration>(configuration, UploadIntentConfiguration.SectionName);
-                .AddOptionsWithValidateOnStart<UploadIntentConfiguration>()
-                .Bind(configuration.GetRequiredSection(UploadIntentConfiguration.SectionName))
-                .ValidateDataAnnotations();
-
-            serviceDescriptors.AddSingleton(serviceProvider =>
-                serviceProvider.GetRequiredService<IOptions<UploadIntentConfiguration>>().Value);
-
-            serviceDescriptors.AddScoped<UploadIntentValidator>();
 
             return serviceDescriptors;
         }

backend/Musify.Worker/Program.cs

@@ -10,9 +10,9 @@ var configuration = builder.Configuration;
 
 var services = builder.Services;
 
-services.AddApplicationStorageConfiguration(configuration);
+services.AddValidatedOptions<ApplicationStorageConfiguration>(configuration, ApplicationStorageConfiguration.SectionName);
-services.AddPlayListConfiguration(configuration);
+services.AddValidatedOptions<PlayListConfiguration>(configuration, PlayListConfiguration.SectionName);
-services.AddTrackConfiguration(configuration);
+services.AddValidatedOptions<TrackConfiguration>(configuration, TrackConfiguration.SectionName);
 services.AddStorageService(configuration);
 services.AddAudioTranscoder(configuration);
 services.AddPictureService(configuration);