drupal/core/modules/block_content/block_content.install

<?php

/**
 * @file
 * Install, update and uninstall functions for the block_content module.
 */

use Drupal\Core\Entity\Form\RevisionDeleteForm;
use Drupal\Core\Entity\Form\RevisionRevertForm;
use Drupal\Core\Entity\Routing\RevisionHtmlRouteProvider;
use Drupal\Core\StringTranslation\TranslatableMarkup;

/**
 * Implements hook_update_last_removed().
 */
function block_content_update_last_removed() {
  return 8600;
}

/**
 * Update entity definition to handle revision routes.
 */
function block_content_update_10100(&$sandbox = NULL): TranslatableMarkup {
  $entityDefinitionUpdateManager = \Drupal::entityDefinitionUpdateManager();
  $definition = $entityDefinitionUpdateManager->getEntityType('block_content');
  $routeProviders = $definition->get('route_provider');
  $routeProviders['revision'] = RevisionHtmlRouteProvider::class;
  $definition
    ->setFormClass('revision-delete', RevisionDeleteForm::class)
    ->setFormClass('revision-revert', RevisionRevertForm::class)
    ->set('route_provider', $routeProviders)
    ->setLinkTemplate('revision-delete-form', '/block/{block_content}/revision/{block_content_revision}/delete')
    ->setLinkTemplate('revision-revert-form', '/block/{block_content}/revision/{block_content_revision}/revert')
    ->setLinkTemplate('version-history', '/block/{block_content}/revisions');
  $entityDefinitionUpdateManager->updateEntityType($definition);
  return \t('Added revision routes to Custom block entity type.');
}

/**
 * Remove the unique values constraint from block content info fields.
 */
function block_content_update_10200() {
  $constraint = 'UniqueField';
  $definition_update_manager = \Drupal::entityDefinitionUpdateManager();
  $field_storage_definition = $definition_update_manager->getFieldStorageDefinition('info', 'block_content');
  $constraints = $field_storage_definition->getConstraints();
  if (isset($constraints[$constraint])) {
    unset($constraints[$constraint]);
    $field_storage_definition->setConstraints($constraints);
    $definition_update_manager->updateFieldStorageDefinition($field_storage_definition);
  }
}