Document how to programmatically create a layout, or how to deploy layouts from one environment to another

WIP - seems to work.

use Drupal\layout_builder\Section;
use Drupal\layout_builder\SectionComponent;
use Drupal\layout_library\Entity\Layout;

/**
 * Create a new layout for Landing Pages.
 */
function MYMODULE_deploy_10000() {
  // This layout contains two sections - the first one has the moderation
  // control widget while the second one contains the actual page content. It
  // also uses two section layouts - cores "layout_onecol" and a custom one
  // named "landing_page_general".
  //
  // Layouts are created by first creating the layout object. Inside the layout
  // are sections, and inside each section are components.

  // Need the UUID service to create new UUIDs for the components that are added
  // to the sections.
  $uuid = \Drupal::service('uuid');

  // Start off by creating a layout.
  $layout = Layout::create([
    'id' => 'improved',
    'label' => 'Improved formatting',
    'targetEntityType' => 'node',
    'targetBundle' => 'landing_page',
  ]);

  // Add the first section with the moderation control widget.
  $section1 = new Section('layout_onecol');
  $section1->setLayoutSettings([
    'label' => 'Admin region',
  ]);
  $component = new SectionComponent(
    $uuid->generate(), 'content', [
      'id' => 'extra_field_block:node:landing_page:content_moderation_control',
      'label' => 'Moderation control',
      'label_display' => FALSE,
      'provider' => 'layout_builder',
      'context_mapping' => [
        'entity' => 'layout_builder.entity',
      ],
      'settings' => [],
      'third_party_settings' => [],
    ]
  );
  $section1->appendComponent($component);

  // Add the first section to the layout.
  $layout->appendSection($section1);

  // Add the second section which contains the actual page content.
  $section2 = new Section('landing_page_general');
  $section2->setLayoutSettings([
    'label' => 'Page content',
  ]);
  $component = new SectionComponent(
    $uuid->generate(), 'title', [
      'id' => 'field_block:node:landing_page:title',
      'label' => 'Title',
      'label_display' => FALSE,
      'provider' => 'layout_builder',
      'context_mapping' => [
        'entity' => 'layout_builder.entity',
        'view_mode' => 'view_mode',
      ],
      'formatter' => [
        'type' => 'string',
        'label' => 'hidden',
        'settings' => [
          'link_to_entity' => FALSE,
        ],
        'third_party_settings' => [],
      ],
    ]
  );
  $section2->appendComponent($component);
  $component = new SectionComponent(
    $uuid->generate(), 'main', [
      'id' => 'field_block:node:landing_page:body',
      'label' => 'Body',
      'label_display' => FALSE,
      'provider' => 'layout_builder',
      'context_mapping' => [
        'entity' => 'layout_builder.entity',
        'view_mode' => 'view_mode',
      ],
      'formatter' => [
        'type' => 'text_default',
        'label' => 'hidden',
        'settings' => [],
        'third_party_settings' => [],
      ],
    ]
  );
  $section2->appendComponent($component);
  $component = new SectionComponent(
    $uuid->generate(), 'contact', [
      'id' => 'views_block:contact_us-block_1',
      'label' => '',
      'label_display' => FALSE,
      'provider' => 'views',
      'context_mapping' => [],
      'views_label' => '',
      'items_per_page' => 'none',
    ]
  );
  $section2->appendComponent($component);

  // Add the second section to the layout.
  $layout->appendSection($section2);

  // Save the layout.
  $layout->save();
}