OpenAPI servers not auto-generated when root_path is set

[duckontheweb]

As of fastapi/fastapi#1596 FastAPI will autogenerate the servers section of the OpenAPI document if the FastAPI instance has a root_path set. This is crucial in setting up the right routes in things like the "Try it out" section of the Swagger docs page.
Because stac-fastapi customizes the FastAPI.openapi method and does not pass the servers argument through, this section of the docs does not get autogenerated as it should.

The signature of StacAPI.customize_openapi should probably be updated to pass through all of the same arguments as the default FastAPI.openapi method.

def openapi(self) -> Dict[str, Any]:
    if not self.app.openapi_schema:
        self.openapi_schema = get_openapi(
            title=self.title,
            version=self.api_version,
            openapi_version=self.app.openapi_version,
            description=self.description,
            terms_of_service=self.app.terms_of_service,
            contact=self.app.contact,
            license_info=self.app.license_info,
            routes=self.app.routes,
            tags=self.app.openapi_tags,
            servers=self.app.servers,
        )
    return self.app.openapi_schema