openapi-response-validator: add ajv options

[sshahar1]

This PR allow pass extra options to Ajv validator for example to allow using a discriminator.
It is equivalent to the requests PR #709

[jsdevel]

@sshahar1 plz add some tests

[sshahar1]

@sshahar1 plz add some tests

Hi @jsdevel From what I see all the tests in the repo are data-driven and not based on this class, I also saw that the original PR didn't have tests. Is it okay that I add a new technique here?

[jsdevel]

@sshahar1 you should be able to add a new test pretty easily. i'd like to see this solid and not regress.

[sshahar1]

@sshahar1 you should be able to add a new test pretty easily. i'd like to see this solid and not regress.

Okay, I'll update my PR. Thanks

[sshahar1]

@jsdevel Hi, I figured out the test driven use cases and added 2 tests