Add audit logs.

API/ROLAC.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -0,0 +1,78 @@
+using System.Text.Json;
+using Microsoft.AspNetCore.Mvc;
+
+namespace ROLAC.API.Middleware;
+
+/// <summary>
+/// Catches any unhandled exception from the downstream pipeline, logs it (which flows through
+/// the DB sink into SystemLogs at Error level with full stack + StatusCode 500), and returns a
+/// clean RFC7807 problem+json response. Stack traces are never leaked to the client outside
+/// Development. Registered as the FIRST middleware so it also catches auth/authorization faults.
+/// </summary>
+public sealed class ExceptionHandlingMiddleware
+{
+    private readonly RequestDelegate _next;
+    private readonly ILogger<ExceptionHandlingMiddleware> _logger;
+    private readonly IHostEnvironment _env;
+
+    public ExceptionHandlingMiddleware(
+        RequestDelegate next, ILogger<ExceptionHandlingMiddleware> logger, IHostEnvironment env)
+    {
+        _next   = next;
+        _logger = logger;
+        _env    = env;
+    }
+
+    public async Task InvokeAsync(HttpContext context)
+    {
+        try
+        {
+            await _next(context);
+        }
+        catch (OperationCanceledException) when (context.RequestAborted.IsCancellationRequested)
+        {
+            // The client went away — not a server error; don't log as 500.
+            return;
+        }
+        catch (Exception ex)
+        {
+            await HandleAsync(context, ex);
+        }
+    }
+
+    private async Task HandleAsync(HttpContext context, Exception exception)
+    {
+        // Logged here → picked up by the DB sink (Error ≥ Warning floor) with full ex.ToString().
+        _logger.LogError(
+            exception,
+            "Unhandled exception for {Method} {Path} (traceId {TraceId})",
+            context.Request.Method, context.Request.Path, context.TraceIdentifier);
+
+        if (context.Response.HasStarted)
+        {
+            // Too late to write a clean body; the log row above is still captured.
+            return;
+        }
+
+        var problem = new ProblemDetails
+        {
+            Status = StatusCodes.Status500InternalServerError,
+            Title  = "An unexpected error occurred.",
+            Type   = "https://tools.ietf.org/html/rfc7231#section-6.6.1",
+        };
+        problem.Extensions["traceId"] = context.TraceIdentifier;
+        if (_env.IsDevelopment())
+            problem.Detail = exception.ToString();
+
+        context.Response.Clear();
+        context.Response.StatusCode  = StatusCodes.Status500InternalServerError;
+        context.Response.ContentType = "application/problem+json";
+
+        await context.Response.WriteAsync(JsonSerializer.Serialize(problem, JsonSerializerOptions));
+    }
+
+    private static readonly JsonSerializerOptions JsonSerializerOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+    };
+}