Support HTTP prefer async with OpenAPI

[jfallows]

Describe the desired outcome from the user's perspective
As an API owner, I want to define an async path in my OpenAPI spec, and have the work with http-kafka mapping in zilla.

Acceptance criteria

• Specifying prefer: respond-async in the HTTP request for POST to create a Pet in PetStore OpenAPI endpoint, returns 202 accepted with location header
• Following up with a GET request to the returned location gives either the response (if complete) or another 202 if not yet complete

Additional context
None

Tasks

• Define PetStore OpenAPI endpoint supporting prefer: respond-async and 202
• Support mapping of async OpenAPI endpoint to http-kafka config in openapi binding