Configurable cache'ing of OpenAPI instances

[piotrp]

Is your feature request related to a problem? Please describe.
I want to filter returned OpenAPI operations by using logged-in user's permissions - hide administrative endpoints from end-users, while still allowing application administrators to view them. Currently I'm running with disabled cache, but building OpenAPI definitions is expensive ("Init duration for springdoc-openapi" reports between 500 and 1000ms on my laptop) and I'd like to optimize this.

Describe the solution you'd like
A way to customize cache'ing, basically override get/set methods on OpenAPIService.cachedOpenAPI. Or making constructor of OpenAPIService public so that I can provide custom implementation.

Describe alternatives you've considered
A separate GroupedOpenApi instances, but this would require dynamic filtering of /metadata/{group} (MultipleOpenApiWebMvcResource) and /metadata (SwaggerConfigResource).