Add feature to set global default for any Option to not be nullable

[frederikrothenberger]

Hi

In #1248 the default behaviour was changed to no longer set optional query parameters as nullable. We would like this behaviour to apply globally to any Option.

I.e. change this logic to default to nullable false.

Would it be possible to have some global way of setting this preference once and have it apply to the whole api spec?

Depending on the effort required, I might be able to contribute that feature, if you agree that it would be useful.

This would probably also address the feedback raised in #1260.