[Request] OpenAPI schema annotations

### Describe the feature

https://download.eclipse.org/microprofile/microprofile-open-api-2.0/microprofile-openapi-spec-2.0.html#_annotations

Currently the OpenAPI schema is quite barren. Since it is autogenerated from annotation processing on the sources it does correctly list all of the endpoints and mostly documents the expected parameters, response codes, and response format, etc., though there are some apparent gaps here and there where source analysis doesn't see the full picture. It would also be good to add some nice human-friendly descriptions of what endpoints are intended to do, as a reference for developers.

### Anything other information?

_No response_

Start by reading the MicroProfile OpenAPI 2.0 annotations section linked in the issue, then inspect the Java sources used for annotation processing and the generated OpenAPI schema. Compare the documented endpoints, parameters, response codes, and response formats with the source, and identify where human-friendly endpoint descriptions and missing schema details are needed. Done means the generated schema includes the intended annotations and descriptions.

Written by the indexing model from the issue text.