fix: add RequestDelegate to ExceptionMiddleware constructor

The middleware was using primary constructor syntax but was missing
the RequestDelegate next parameter, causing dependency injection to
fail at runtime with InvalidOperationException.

Fixed by adding RequestDelegate next as the first parameter in the
primary constructor and removing it from InvokeAsync method signature,
which is the correct pattern for ASP.NET Core middleware.

Author: nanotaboada

src/Dotnet.Samples.AspNetCore.WebApi/Middlewares/ExceptionMiddleware.cs

@@ -8,7 +8,11 @@ namespace Dotnet.Samples.AspNetCore.WebApi.Middlewares;
 /// <summary>
 /// Middleware for global exception handling with RFC 7807 Problem Details format.
 /// </summary>
-public class ExceptionMiddleware(ILogger<ExceptionMiddleware> logger, IHostEnvironment environment)
+public class ExceptionMiddleware(
+    RequestDelegate next,
+    ILogger<ExceptionMiddleware> logger,
+    IHostEnvironment environment
+)
 {
     private const string ProblemDetailsContentType = "application/problem+json";
 
@@ -18,7 +22,7 @@ public class ExceptionMiddleware(ILogger<ExceptionMiddleware> logger, IHostEnvir
     /// <summary>
     /// Invokes the middleware to handle exceptions globally.
     /// </summary>
-    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
+    public async Task InvokeAsync(HttpContext context)
     {
         try
         {