Note:
- in generated C# clients code using NSwag, the behavior is that if the error (4xx) status code is documented, then ApiException<ProblemDetails> is returned instead of ProblemDetails in response and if the status code is not documented and requires reference to the original ProblemDetails structure and maybe Helland.ErrorDetails in case of exception stack traces being sent as well, 
in case of non-documented error codes, ProblemDetails is returned in response and is to be deserialized and does not require ProblemDetails from specific assembly.