Add layout builder support for the Services blocks

[andybroomfield]

When using layout builder with service content types, there's a case for adding the blocks into the layout (although custom field formatters would be better).

The Service CTA blocks, Related topics and Related links blocks don't work correctly inside layout builder. They rely on the current page route to work out the node id, without this the blocks fail as $this->node is not set and an empty check is needed to avoid a WSOD when adding the block.

A node context should be provided for these blocks (in ServiceBlockBase?) This allows the blocks to work with live preview and layout builder instead of displaying 'placeholder for'

.

[andybroomfield]

Going to try and revive this one post beta to work out what the blockers where.
I think we need to get an update hook for the existing blocks so they add the node context so will still display in the block screen, but that might just be a load and save operation.

[andybroomfield]

So the blocker will be that sites block config for service blocks will need to be updated and resaved to add the context.
See https://drupal.stackexchange.com/a/297721 for how.

$entity_type_manager = \Drupal::entityTypeManager();
$blocks = $entity_type_manager->getStorage('block')->loadByProperties([
  'plugin' => 'SERVICE_BLOCK_PLUGIN_ID',
]);

foreach ($blocks as $block) {
  if ($block->getRegion() == 'my_region') {
    $settings = $block->get('settings');
    // modify settings
    $block->set('settings', $settings);
    $block->save();
  }
}

It needs node: '@node.node_route_context:node' adding as a context mapping eg.

settings:
  id: localgov_services_related_links_block
  label: 'Service page related links'
  label_display: '0'
  provider: localgov_services_page
  context_mapping:
    node: '@node.node_route_context:node'