block_content_help($route_name, RouteMatchInterface $route_match) Implements

block_content_theme($existing, $type, $theme, $path) Implements

block_content_entity_type_alter(array &$entity_types) Implements

Allows the creation of custom blocks through the user interface. File core/modules/block_content/block_content

block_content_add_body_field($block_type_id, $label = 'Body') Adds the default body field to a custom block