FileUsageInterface::add() and ::delete() have incorrect param documentation

Problem/Motivation

The documentation for the method ::add() of the FileUsageInterface states:

  /**
   * Records that a module is using a file.
   *
   * Examples:
   * - A module that associates files with nodes, so $type would be
   *   'node' and $id would be the node's nid. Files for all revisions are
   *   stored within a single nid.
   * - The User module associates an image with a user, so $type would be 'user'
   *   and the $id would be the user's uid.
   *
   * @param \Drupal\file\FileInterface $file
   *   A file entity.
   * @param string $module
   *   The name of the module using the file.
   * @param string $type
   *   The type of the object that contains the referenced file.
   * @param int $id
   *   The unique, numeric ID of the object containing the referenced file.
   * @param int $count
   *   (optional) The number of references to add to the object. Defaults to 1.
   */
  public function add(FileInterface $file, $module, $type, $id, $count = 1);

The documentation for the parameter $id (refering to an int value) does not correspond to its schema:

/**
 * Implements hook_schema().
 */
function file_schema() {
  $schema['file_usage'] = array(
    'description' => 'Track where a file is used.',
    'fields' => array(

      // ...

      'id' => array(
        'description' => 'The primary key of the object using the file.',
        'type' => 'varchar_ascii',
        'length' => 64,
        'not null' => TRUE,
        'default' => 0,
      ),

      // ...

The same applies for the ::delete() method.

Proposed resolution

Change the docblock to inform that the parameter $id can be any string.

Remaining tasks

- Review patch

User interface changes

- None

API changes

- None

Data model changes

- None