Add Domain project and shifted handlers to application.

wolverine/a-frame-architecture/FinancialApi/DomainExceptionHandler.cs

@@ -0,0 +1,32 @@
+using Microsoft.AspNetCore.Diagnostics;
+using Microsoft.AspNetCore.Mvc;
+
+namespace FinancialApi;
+
+public class DomainExceptionHandler : IExceptionHandler
+{
+    public async ValueTask<bool> TryHandleAsync(
+        HttpContext httpContext, 
+        Exception exception, 
+        CancellationToken cancellationToken)
+    {
+        // Only intercept our specific domain/validation exceptions
+        if (exception is InvalidOperationException or ArgumentException)
+        {
+            var problemDetails = new ProblemDetails
+            {
+                Status = StatusCodes.Status400BadRequest,
+                Title = "Domain Validation Error",
+                Detail = exception.Message,
+                Type = "https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.1"
+            };
+
+            httpContext.Response.StatusCode = problemDetails.Status.Value;
+            await httpContext.Response.WriteAsJsonAsync(problemDetails, cancellationToken);
+            
+            return true;
+        }
+
+        return false; 
+    }
+}