Utoipa OpenAPI Schemas crate Feature

[Srylax]

As a crate user
I want to use openapi schemas
so that I can convert between AsyncAPI and OpenAPI seemless

Provide a detailed description of the proposed feature

Add a crate Features which allows to switch between OpenAPI and AsyncAPI schemas.
As they are currently the same, there should be no difference between the generated spec.

Alternatives you've considered

Implement From traits for the both schemas