Exceptions re-thrown on subsequent document accesses get their stack traces erased

[LordJZ]

Basically doing throw exceptionThatHasBeenCreatedMuchEarlier; is a big no-no, but this is what happens here:

NSwag/src/NSwag.AspNetCore/Middlewares/OpenApiDocumentMiddleware.cs

Line 89 in 4e94b9d

throw document.Item2;

ExceptionDispatchInfo should be used instead. I will try to submit a PR for this.