Use JavaDoc for JSON Schema and @OpenApi summary & description

**Describe the feature**

It would be cool if it would automagically process JavaDoc (with a doclet) and use it for JSON Schema and OpenAPI summary & descriptions.

**Additional context**

https://springdoc.org/#javadoc-support does something like that (apparently).

No files or tests are named. Start by reviewing the annotation processor and the linked springdoc Javadoc support, then trace how JSON Schema and OpenAPI summary and description generation currently works. Done means JavaDoc is processed and its content is reflected in both output types.

Written by the indexing model from the issue text.