- Use `OptionalEntity<T>` for nullable returns
- Plain classes (no extends/implements)

### Helper
- Stateless utility classes
- Access via `ComponentUtil.getXyzHelper()`
- Named with "Helper" suffix

### DBFlute Generated Code
```
opensearch/{index}/
├── bsentity/, bsbhv/    # Base classes (DO NOT EDIT)
├── exentity/, exbhv/    # Extended classes (customize here)

     *       <td>{@code /home/user/myproject/target/classes}</td>
     *       <td>No explicit path → use output directory</td>
     *     </tr>
     *     <tr>
     *       <td>{@code Optional.of(Path.of("META-INF"))}</td>
     *       <td>{@code /home/user/myproject/target/classes}</td>
     *       <td>{@code /home/user/myproject/target/classes/META-INF}</td>

            // Each extract will overwrite the top level classes that existed before it, the result is that we end up
            // with a single version of the class in `jarExpandDir`.
            // This will be the closes version to `targetCompatibility`, the same class that would be loaded in a JVM
            // that has `targetCompatibility` version.

  @VisibleForTesting
  List<Class<?>> findClassesToTest(
      Iterable<? extends Class<?>> classes, Iterable<String> explicitTestNames) {
    // "a.b.Foo" -> a.b.Foo.class
    TreeMap<String, Class<?>> classMap = Maps.newTreeMap();
    for (Class<?> cls : classes) {
      classMap.put(cls.getName(), cls);
    }
    // Foo.class -> [FooTest.class, FooTests.class, FooTestSuite.class, ...]

    assertThat(findClassesToTest(classes, "testNotThere", "testPublic")).isEmpty();
  }

  public void testFindClassesToTest_withCorrespondingTestClass_noTestName() {
    assertThat(findClassesToTest(ImmutableList.of(Foo.class, FooTest.class)))
        .containsExactly(Foo.class);
  }

  static class EmptyTestCase {}

  static class EmptyTest {}

  static class EmptyTests {}

        ).buildAndFail();

        assertTaskFailed(result, ":absurd");
        assertOutputContains(result.getOutput(), "Classes with violations:", "  * TestingIO", "> Audit of third party dependencies failed");
        assertOutputMissing(result.getOutput(), "Missing classes:");
        assertNoDeprecationWarning(result);
    }

    public void testClassNotFoundAndCompileOnlyIgnored() {

     */
    private static boolean isApplicable(Method method, Class<?>... classes) {
        Class<?>[] methodArgs = method.getParameterTypes();

        if (methodArgs.length != classes.length) {
            return false;
        }

        for (int i = 0; i < classes.length; ++i) {
            if (!isMethodInvocationConvertible(methodArgs[i], classes[i])) {
                return false;
            }
        }

        kryo.register(Byte.class);
        kryo.register(byte[].class);
        kryo.register(Short.class);
        kryo.register(short[].class);
        kryo.register(Character.class);
        kryo.register(char[].class);

        // Common object types
        kryo.register(Object.class);
        kryo.register(Object[].class);
        kryo.register(Class.class);

        // Date and time types

     * </p>
     *
     * @param className the class name
     * @return <code>true</code> if the class file exists in the resources handled by this instance
     */
    boolean isExistClass(final String className);

    /**
     * Searches for classes handled by this instance and calls the handler for each class.
     * <p>
     * If a root package is specified at instance construction, only classes under the root package are targeted.
     * </p>

    }

    @Test
    void testTargetPath() {
        Build build = mock(Build.class);
        when(build.getDirectory()).thenReturn("target");
        when(build.getOutputDirectory()).thenReturn("target/classes");
        when(build.getTestOutputDirectory()).thenReturn("target/test-classes");

        Project project = mock(Project.class);
        when(project.getBuild()).thenReturn(build);