Refactor ExceptionHandlingMiddleware responses

Refactored `ExceptionHandlingMiddleware` to use `ValidationProblemDetails` for structured and consistent error responses. Marked the middleware as obsolete with a recommendation to use `DigitalData.Core.Exceptions.Middleware`. Updated exception handling logic to replace error message strings with detailed problem descriptions, including titles and details for each exception type. Improved the default case for unhandled exceptions with a user-friendly message. Enhanced response serialization using `WriteAsJsonAsync`.

src/ReC.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -11,7 +11,7 @@ namespace ReC.API.Middleware;
 /// <summary>
 /// Middleware for handling exceptions globally in the application.
 /// Captures exceptions thrown during the request pipeline execution,
-/// logs them, and returns an appropriate HTTP response with a JSON error message.
+/// logs them, and returns an appropriate HTTP response with a JSON error details.
 /// </summary>
 [Obsolete("Use DigitalData.Core.Exceptions.Middleware")]
 public class ExceptionHandlingMiddleware
@@ -58,13 +58,17 @@ public class ExceptionHandlingMiddleware
     {
         context.Response.ContentType = "application/json";
 
-        string? message = null;
+        ValidationProblemDetails? details = null;
 
         switch (exception)
         {
             case BadRequestException badRequestEx:
                 context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
-                message = badRequestEx.Message;
+                details = new() 
+                { 
+                    Title = "Bad Request", 
+                    Detail = badRequestEx.Message 
+                };
                 break;
 
             case ValidationException validationEx:
@@ -74,37 +78,46 @@ public class ExceptionHandlingMiddleware
                     .GroupBy(e => e.PropertyName, e => e.ErrorMessage)
                     .ToDictionary(failureGroup => failureGroup.Key, failureGroup => failureGroup.ToArray());
 
-                await context.Response.WriteAsJsonAsync(new ValidationProblemDetails()
+                details = new ValidationProblemDetails()
                 {
                     Title = "Validation failed",
                     Errors = validationEx.Errors
                         .GroupBy(e => e.PropertyName, e => e.ErrorMessage)
                         .ToDictionary(failureGroup => failureGroup.Key, failureGroup => failureGroup.ToArray()),
-                });
+                };
 
                 break;
 
             case NotFoundException notFoundEx:
                 context.Response.StatusCode = (int)HttpStatusCode.NotFound;
-                message = notFoundEx.Message;
+                details = new() 
+                {
+                    Title = "Not Found",
+                    Detail = notFoundEx.Message
+                };
                 break;
 
             case DataIntegrityException dataIntegrityEx:
                 context.Response.StatusCode = (int)HttpStatusCode.Conflict;
-                message = dataIntegrityEx.Message;
+                details = new() 
+                {
+                    Title = "Data Integrity Violation",
+                    Detail = dataIntegrityEx.Message
+                };
                 break;
 
             default:
                 logger.LogError(exception, "Unhandled exception occurred.");
                 context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
-                message = "An unexpected error occurred.";
+                details = new()
+                {
+                    Title = "Internal Server Error",
+                    Detail = "An unexpected error occurred. Please try again later."
+                };
                 break;
         }
 
-        if (message is not null)
-            await context.Response.WriteAsync(JsonSerializer.Serialize(new
-            {
-                message
-            }));
+        if (details is not null)
+            await context.Response.WriteAsJsonAsync(details);
     }
 }