public void pluginExtension(Action<? super ExtensionParameters> action) {
    ExtensionParameters extension = objectFactory.newInstance(ExtensionParameters.class);
    action.execute(extension);
    pluginExtensions.add(extension);
  }
Adds a new plugin extension configuration to the extensions list.

@param action closure representing an extension configuration
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/ExtensionParametersSpec.java