Integrate Serilog and add configuration classes

Enhanced logging with Serilog, including request logging and
structured exception handling during startup. Added support
for the Options Pattern with new configuration classes:
`DocumentOperatorSettings`, `RedisSettings`, and
`ApiKeySettings`. Introduced `TenantInfo` class for tenant
management. Updated project files to include new dependencies
and removed unused `Configuration` folder reference.

DocumentOperator.API/DocumentOperator.API.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFramework>net8.0</TargetFramework>
@@ -10,6 +10,8 @@
     <PackageReference Include="Asp.Versioning.Http" Version="8.1.1" />
     <PackageReference Include="Microsoft.Extensions.Caching.StackExchangeRedis" Version="8.0.28" />
     <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
+    <PackageReference Include="Serilog.Enrichers.Environment" Version="3.0.1" />
+    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />
   </ItemGroup>
 

DocumentOperator.API/Program.cs

@@ -1,25 +1,72 @@
+using Serilog;
+using DocumentOperator.Infrastructure.Configuration;
+
 var builder = WebApplication.CreateBuilder(args);
 
-// Add services to the container.
+// ========================================
+// 1. Serilog Configuration
+// ========================================
+Log.Logger = new LoggerConfiguration()
+    .ReadFrom.Configuration(builder.Configuration)
+    .Enrich.FromLogContext()
+    .Enrich.WithProperty("Application", "DocumentOperator")
+    .CreateLogger();
 
-builder.Services.AddControllers();
+builder.Host.UseSerilog();
-// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
-builder.Services.AddEndpointsApiExplorer();
-builder.Services.AddSwaggerGen();
 
-var app = builder.Build();
+Log.Information("Starting DocumentOperator API...");
 
-// Configure the HTTP request pipeline.
+try
-if (app.Environment.IsDevelopment())
 {
-    app.UseSwagger();
+    // ========================================
-    app.UseSwaggerUI();
+    // 2. Options Pattern Configuration
+    // ========================================
+    builder.Services.Configure<DocumentOperatorSettings>(
+        builder.Configuration.GetSection(DocumentOperatorSettings.SectionName));
+
+    builder.Services.Configure<RedisSettings>(
+        builder.Configuration.GetSection(RedisSettings.SectionName));
+
+    builder.Services.Configure<ApiKeySettings>(
+        builder.Configuration.GetSection(ApiKeySettings.SectionName));
+
+    // ========================================
+    // 3. Services
+    // ========================================
+    builder.Services.AddControllers();
+    builder.Services.AddEndpointsApiExplorer();
+    builder.Services.AddSwaggerGen();
+
+    // ========================================
+    // 4. Build App
+    // ========================================
+    var app = builder.Build();
+
+    // ========================================
+    // 5. Middleware Pipeline
+    // ========================================
+    if (app.Environment.IsDevelopment())
+    {
+        app.UseSwagger();
+        app.UseSwaggerUI();
+    }
+
+    app.UseSerilogRequestLogging(); // Log HTTP Requests
+
+    app.UseHttpsRedirection();
+    app.UseAuthorization();
+    app.MapControllers();
+
+    Log.Information("DocumentOperator API started successfully");
+
+    app.Run();
+}
+catch (Exception ex)
+{
+    Log.Fatal(ex, "Application startup failed");
+    throw;
+}
+finally
+{
+    Log.CloseAndFlush();
 }
-
-app.UseHttpsRedirection();
-
-app.UseAuthorization();
-
-app.MapControllers();
-
-app.Run();

DocumentOperator.Infrastructure/Configuration/ApiKeySettings.cs

@@ -0,0 +1,9 @@
+namespace DocumentOperator.Infrastructure.Configuration;
+
+public class ApiKeySettings
+{
+    public const string SectionName = "ApiKeySettings";
+
+    public bool EnableValidation { get; set; } = true;
+    public Dictionary<string, TenantInfo> Keys { get; set; } = new();
+}

DocumentOperator.Infrastructure/Configuration/DocumentOperatorSettings.cs

@@ -0,0 +1,11 @@
+namespace DocumentOperator.Infrastructure.Configuration;
+
+public class DocumentOperatorSettings
+{
+    public const string SectionName = "DocumentOperatorSettings";
+
+    public string TempFolderPath { get; set; } = string.Empty;
+    public int TempFileRetentionHours { get; set; }
+    public int MaxPdfSizeMB { get; set; }
+    public bool EnableDetailedLogging { get; set; }
+}

DocumentOperator.Infrastructure/Configuration/RedisSettings.cs

@@ -0,0 +1,10 @@
+namespace DocumentOperator.Infrastructure.Configuration;
+
+public class RedisSettings
+{
+    public const string SectionName = "RedisSettings";
+
+    public string ConnectionString { get; set; } = "localhost:6379";
+    public string InstanceName { get; set; } = "DocumentOperator:";
+    public int CacheExpirationMinutes { get; set; } = 60;
+}

DocumentOperator.Infrastructure/Configuration/TenantInfo.cs

@@ -0,0 +1,8 @@
+namespace DocumentOperator.Infrastructure.Configuration;
+
+public class TenantInfo
+{
+    public string TenantId { get; set; } = string.Empty;
+    public string TenantName { get; set; } = string.Empty;
+    public bool IsActive { get; set; } = true;
+}

DocumentOperator.Infrastructure/DocumentOperator.Infrastructure.csproj

@@ -17,7 +17,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <Folder Include="Configuration\" />
     <Folder Include="DependencyInjection\" />
     <Folder Include="Services\FileStorage\" />
     <Folder Include="Services\DocumentValidation\" />