[Feature Request] Please provide official way to integrate swagger2 + openAPI.

Grails `rest-api` profile can help me developed my restful service very fast. I hope grails can provide official way to integrate swagger2 + openAPI (Maybe plugin is better).

I find a [springfox-grails-integration](https://github.com/springfox/springfox-grails-integration) project can do this. But this project is a little lack of maintenance, and the maintenance is not familiar with Grails, and not support Grails 3.3 until now.

Would you please provide an official way to integrate swagger2 + openAPI?

Thanks.

Start by reviewing the Grails `rest-api` profile and the linked `springfox-grails-integration` project, especially its support for Grails 3.3. Define what an official Swagger 2 and OpenAPI integration should provide and how it would be maintained; done means an agreed, supported integration path for Grails.

Written by the indexing model from the issue text.