Add integration with Starlette

[sisp]

Starlette is a quite popular ASGI library, in part because it's at the core of the (to me somewhat surprisingly) vastly popular FastAPI project. Since I believe in the spec-first approach (contrary to FastAPI) and in the architectural design of openapi-core, I think it would be great to add an integration with Starlette.

[p1c2u]

I was thinking about it. I would go even further and try to integrate with FastAPI itself as an alternative to built-in approach.

[sisp]

Hm, I haven't thought about the technical details, but perhaps it's possible to have both because FastAPI is built on top of Starlette? Perhaps via a Starlette middleware like it's done for other sane web frameworks. I'm a bit sceptical about FastAPI to be honest. Starlette looks very clean and modular though.

[sisp]

Awesome, thanks for adding support for Starlette so quickly, @p1c2u! 🙏 🎉