<type>String</type>
        </field>
      </fields>
    </class>
    <class>
      <name>Extension</name>
      <version>4.0.0+</version>
      <description>Describes a build extension to utilise.</description>
      <fields>
        <field>
          <name>groupId</name>
          <version>4.0.0+</version>
          <description>The group ID of the extension's artifact.</description>