Start enabling openapi 3.1

[pmlopes]

Signed-off-by: Paulo Lopes [email protected]

Motivation:

Explain here the context, and why you're making that change, what is the problem you're trying to solve.

Conformance:

Your commits should be signed and you should have signed the Eclipse Contributor Agreement as explained in https://github.com/eclipse/vert.x/blob/master/CONTRIBUTING.md Please also make sure you adhere to the code style guidelines: https://github.com/vert-x3/wiki/wiki/Vert.x-code-style-guidelines