[BUG] [csharp] DefaultExceptionFactory hides exceptions

Created by: chrbkr

The openapi-generator creates this ExceptionFactory:

https://github.com/OpenAPITools/openapi-generator/blob/150e24dc553a8ea5230ffb938ed3e6020e972faa/samples/client/petstore/csharp/OpenAPIClientNetStandard/src/Org.OpenAPITools/Client/Configuration.cs#L48-L62

First of all, I'm not sure handling response codes as exceptions is good practice, but that could be debated.

However, what's much worse is that real exceptions are hidden - in case a timeout occurs, or the connection is closed etc., all I get is a null response instead of the real exception.

Am I missing something? How are other people handling this?