First draft to support unexpected enum values

[brice-laurencin]

resolves #692

This is a first draft, I would follow the guidelines if you thinks this feature is useful.
I still have an issue with numbered enum that I need to dig into, but I'd like to have a first feedback on this version.

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[github-actions]

🎊 PR Preview 9e15497 has been successfully built and deployed. See the documentation preview: https://quarkus-openapi-generator-preview-pr-700.surge.sh

[mcruzdev]

Hi, @brice-laurencin Thank you for your pull request!

Would be great to have a documentation for our users, to know how to use the new property, WYT?

[brice-laurencin]

Definitely.
This is a first draft to know if I should push the effort further, if you (the maintainers of the extension) think this is valuable.

[ricardozanini]

@brice-laurencin please go ahead!