public static File tempRelativeDir(String root) {
        File rootFile = new File(root);
        if (rootFile.mkdir()) {
            rootFile.deleteOnExit();
        }
        return tempDirectory(rootFile.toPath(), null);
    }
Create a temporary directory under the given root directory.
The root directory is removed on JVM exit if it doesn't already exist
when this function is invoked.

@param root path to create temporary directory under
@return the temporary directory created within {@code root}
clients/src/test/java/org/apache/kafka/test/TestUtils.java