Enhance Swagger UI with Negotiate auth and XML docs

- Add custom OpenAPI doc with title, version, and description
- Define "Negotiate" security scheme for NTLM/Kerberos auth
- Require Negotiate authentication for all endpoints in Swagger
- Include XML comments in Swagger UI if available
- Configure Swagger UI to send credentials (withCredentials: true) for authenticated endpoint testing

FakeNTLMServer.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk.Web">
+<Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
     <TargetFramework>net8.0</TargetFramework>

Program.cs

@@ -1,4 +1,5 @@
 using Microsoft.AspNetCore.Authentication.Negotiate;
+using Microsoft.OpenApi.Models;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -11,7 +12,42 @@ builder.Services.AddAuthentication(NegotiateDefaults.AuthenticationScheme)
 builder.Services.AddAuthorization();
 // Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
 builder.Services.AddEndpointsApiExplorer();
-builder.Services.AddSwaggerGen();
+builder.Services.AddSwaggerGen(options =>
+{
+    options.SwaggerDoc("v1", new OpenApiInfo
+    {
+        Title = "FakeNTLMServer",
+        Version = "v1",
+        Description = "NTLM/Negotiate authentication test server"
+    });
+
+    options.AddSecurityDefinition("Negotiate", new OpenApiSecurityScheme
+    {
+        Type = SecuritySchemeType.Http,
+        Scheme = "Negotiate",
+        Description = "Windows Authentication (NTLM/Kerberos). Credentials are sent automatically by the browser."
+    });
+
+    options.AddSecurityRequirement(new OpenApiSecurityRequirement
+    {
+        {
+            new OpenApiSecurityScheme
+            {
+                Reference = new OpenApiReference
+                {
+                    Type = ReferenceType.SecurityScheme,
+                    Id = "Negotiate"
+                }
+            },
+            Array.Empty<string>()
+        }
+    });
+
+    var xmlFile = $"{System.Reflection.Assembly.GetExecutingAssembly().GetName().Name}.xml";
+    var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
+    if (File.Exists(xmlPath))
+        options.IncludeXmlComments(xmlPath);
+});
 
 var app = builder.Build();
 
@@ -19,7 +55,11 @@ var app = builder.Build();
 if (app.Environment.IsDevelopment())
 {
     app.UseSwagger();
-    app.UseSwaggerUI();
+    app.UseSwaggerUI(options =>
+    {
+        // Enable sending credentials (NTLM tokens) with Swagger UI requests
+        options.ConfigObject.AdditionalItems["withCredentials"] = true;
+    });
 }
 
 app.UseHttpsRedirection();