@Component
public class ApiAuthEntryPoint implements AuthenticationEntryPoint {
    @Override
    public void commence(HttpServletRequest request, HttpServletResponse response, 
                         AuthenticationException authException) throws IOException {
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        response.setContentType("application/json");
        response.getWriter().write("{\"error\": \"Invalid credentials\", \"timestamp\": \"" + Instant.now() + "\"}");
    }
}