feat(jans-config-api): Maintain OpenAPI spec with example payloads

### Description

Some `config-api` endpoints in the Swagger UI do not include prefilled example data. This makes it harder to understand how to use the APIs effectively and slows down testing and development.

### Proposal

Add meaningful example request and response data directly in the OpenAPI annotations. This will:

- Improve Swagger usability
- Help developers understand request/response formats faster
- Support automated testing based on examples

### Suggested Steps

1. Identify endpoints that are missing example data.
2. Add examples using Swagger annotations (e.g., `@Schema`, `@ExampleObject`).
3. Regenerate the OpenAPI spec using:

```bash
mvn -q -f "$MAIN_DIRECTORY_LOCATION"/jans-config-api/pom.xml -DskipTests clean compile