public Path newFolder() throws IOException {
        return delegate.newFolder();
    }
A JUnit {@link Extension} that creates a {@link TemporaryFolder}.

<pre>{@code
> class MyTest {
>     @RegisterExtension
>     static final TemporaryFolderExtension folder = new TemporaryFolderExtension();
>
>     @Test
>     void test() throws Exception {
>         Path file = folder.newFile();
>         ...
>     }
> }
}</pre>
testing-internal/src/main/java/com/linecorp/armeria/internal/testing/TemporaryFolderExtension.java