trait FileFieldCreationTrait

trait FileFieldCreationTrait {
    
    /**
     * Creates a new file field.
     *
     * @param string $name
     *   The name of the new field (all lowercase). The Field UI 'field_' prefix
     *   is not added to the field name.
     * @param string $entity_type
     *   The entity type.
     * @param string $bundle
     *   The bundle that this field will be added to.
     * @param array $storage_settings
     *   A list of field storage settings that will be added to the defaults.
     * @param array $field_settings
     *   A list of instance settings that will be added to the instance defaults.
     * @param array $widget_settings
     *   A list of widget settings that will be added to the widget defaults.
     *
     * @return \Drupal\field\FieldStorageConfigInterface
     *   The file field.
     */
    protected function createFileField($name, $entity_type, $bundle, $storage_settings = [], $field_settings = [], $widget_settings = []) {
        $field_storage = FieldStorageConfig::create([
            'entity_type' => $entity_type,
            'field_name' => $name,
            'type' => 'file',
            'settings' => $storage_settings,
            'cardinality' => !empty($storage_settings['cardinality']) ? $storage_settings['cardinality'] : 1,
        ]);
        $field_storage->save();
        $this->attachFileField($name, $entity_type, $bundle, $field_settings, $widget_settings);
        return $field_storage;
    }
    
    /**
     * Attaches a file field to an entity.
     *
     * @param string $name
     *   The name of the new field (all lowercase). The Field UI 'field_' prefix
     *   is not added to the field name.
     * @param string $entity_type
     *   The entity type this field will be added to.
     * @param string $bundle
     *   The bundle this field will be added to.
     * @param array $field_settings
     *   A list of field settings that will be added to the defaults.
     * @param array $widget_settings
     *   A list of widget settings that will be added to the widget defaults.
     */
    protected function attachFileField($name, $entity_type, $bundle, $field_settings = [], $widget_settings = []) {
        $field = [
            'field_name' => $name,
            'label' => $name,
            'entity_type' => $entity_type,
            'bundle' => $bundle,
            'required' => !empty($field_settings['required']),
            'settings' => $field_settings,
        ];
        FieldConfig::create($field)->save();
        \Drupal::service('entity_display.repository')->getFormDisplay($entity_type, $bundle)
            ->setComponent($name, [
            'type' => 'file_generic',
            'settings' => $widget_settings,
        ])
            ->save();
        // Assign display settings.
        \Drupal::service('entity_display.repository')->getViewDisplay($entity_type, $bundle)
            ->setComponent($name, [
            'label' => 'hidden',
            'type' => 'file_default',
        ])
            ->save();
    }

}