fix: issue where response schemas in the original spec may get overridden

[erunion]

🧰 Changes

This resolves a data corruption bug I discovered in https://github.com/readmeio/api where if you compile the JSON Schema for an operation response with getResponseAsJsonSchema, and somewhere within that response is an example property, we'd update the original API definition object that was supplied to Oas with the examples syntax that getResponseAsJsonSchema reshapes example to -- rendering the original API definition in a non-spec validating state.

🧬 QA & Testing

I added a test that runs getResponseAsJsonSchema against a response in our own spec and then queries the original spec inside the original Oas instance to ensure that the schema property where example was present is only set to examples in the generated JSON Schema.

:upsidedown-cowboy-quadboy:

[julshotal]

ty for adding the validation test!