* {@link CoreExtensions} is validated, but the list elements may have overlapping elements, that requires
     * some logic to sort out (like precedence).
     * <p>
     * The list of {@link CoreExtensions} if present, is in precedence order.
     *
     * @return an {@link Optional} containing the {@link CoreExtensions}, or empty if not configured
     */
    @Nonnull

  xml.namespace="http://maven.apache.org/EXTENSIONS/${version}"
  xml.schemaLocation="https://maven.apache.org/xsd/core-extensions-${version}.xsd">

  <id>core-extensions</id>
  <name>CoreExtensions</name>
  <description><![CDATA[
  <p>This is a reference for the Core Extensions descriptor.</p>
  <p>The default location for the Core Extensions descriptor file is <code>${maven.projectBasedir}/.mvn/extensions.xml</code></p>