@Service("customuserdetails")
public class CustomUserDetails implements UserDetailsService {
    @Autowired
    private UserRepo userrepo;
 
    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {   
        Supplier<UsernameNotFoundException> s= () -> new UsernameNotFoundException("Error finding the user");
        
        User user=userrepo.findByUsername(username).orElseThrow(s);
        return user;
    }}

This is the implementation which is working. I had to change my security beans to @configuration, and I added @repository to my repo interfaces. I also ended up changing my User class to implement UserDetails.