DTO Alter "getUsername" to have links

UserController.java

@RepositoryRestController
public class UserController {
    
    private final RepositoryEntityLinks links;
    private final UserRepository userRepository;
    
    // all arg constructor
    
    @GetMapping("users/search/username")
    public ResponseEntity<Resource<UserUsername>> addLinksToUserUsername(@RequestParam("id") Long id){
    
        Resource<UserUsername> usernameResource = new Resource<>(userRepository.findUsernameById(id));
        
        usernameResource.add(links.linkToSearchResource(User.class, "getUsername").withSelfRel());
        usernameResource.add(links.linkToSingleResource(User.class, id));
        
        return ResponseEntity.ok(usernameResource);
    }
}