Exception handling

Continuing the previous example, if we post a height = 0 into our http://server.localtest.me/headlessApi/TestPage endpoint, and then try to get the TestPage, we would get an invalid operation exception.

However, instead of a Internal Server Error, the HTTP status returned is a Invalid Operation.

The reason is, the exception is intercepted in the src\Litium.AddOns.HeadlessApi\Attributes\ErrorFilterAttribute.cs class, and re-wired as a BadRequest.

You should consider doing the same thing for known errors, as they are not server errors, rather unexpected data.

            switch(actionExecutedContext.Exception)
            {
                //Here we treat known exceptions as BadRequests. 
                //these exceptions are not bugs in code, just that the original request is bad.
                //TODO: handle other known exceptions.
                case DoesNotExistException doesNotExistsException:
                case InvalidOperationException invalidOperationException:
                    actionExecutedContext.Response = actionExecutedContext.Request.CreateErrorResponse(HttpStatusCode.BadRequest, new HttpError(actionExecutedContext.Exception, true));
                    return;
            }