[EC-619] Exceeding seat limit results in vague "Unhandled server error" message (#2558)

* [EC-619] Added 'AggregateException' type to ExceptionHandlerFilter to return error messages in response

* [EC-619] Updated ExceptionHandlerFilterAttribute to return multiple errors using ErrorResponseModel internal property

src/Api/Utilities/ExceptionHandlerFilterAttribute.cs

@@ -92,6 +92,19 @@ public class ExceptionHandlerFilterAttribute : ExceptionFilterAttribute
             errorMessage = "Unauthorized.";
             context.HttpContext.Response.StatusCode = 401;
         }
+        else if (exception is AggregateException aggregateException)
+        {
+            context.HttpContext.Response.StatusCode = 400;
+            var errorValues = aggregateException.InnerExceptions.Select(ex => ex.Message);
+            if (_publicApi)
+            {
+                publicErrorModel = new ErrorResponseModel(errorMessage, errorValues);
+            }
+            else
+            {
+                internalErrorModel = new InternalApi.ErrorResponseModel(errorMessage, errorValues);
+            }
+        }
         else
         {
             var logger = context.HttpContext.RequestServices.GetRequiredService<ILogger<ExceptionHandlerFilterAttribute>>();