[1.0.x] Image 404 Fallback

Thank you for applying!

Before giving links helpful to understand how the review process works, what to expect from a review, and what to do to avoid a review takes more time than needed, I would like to thank all the reviewers for the work they do.
These applications are volunters-driven, which also means it is not possible to predict when an application will be marked fixed and the applicant will get the permission to opt projects into security advisory policy. While we aim to make an application as quick as possible, it is also important for us that more people review the project used for an application. In this way, we make sure applications do not miss some important points that should be instead reported.
Applications are not meant to be complete debugging sessions that eliminate every existing bug, though. I apologize if sometimes applications seem to go into too-detailed reviews.

Please read Review process for security advisory coverage: What to expect for more details and Security advisory coverage application checklist to understand what reviewers look for. Tips for ensuring a smooth review gives some hints for a smoother review.

The important notes are the following.

• If you have not done it yet, you should enable GitLab CI for the project and fix the PHP_CodeSniffer errors/warnings it reports.
• For the time this application is open, only your commits are allowed.
• The purpose of this application is giving you a new drupal.org role that allows you to opt projects into security advisory coverage, either projects you already created, or projects you will create. The project status will not be changed by this application; once this application is closed, you will be able to change the project status from Not covered to Opt into security advisory coverage. This is possible only 14 days after the project is created.
  
  Keep in mind that once the project is opted into security advisory coverage, only Security Team members may change coverage.
• Only the person who created the application will get the permission to opt projects into security advisory coverage. No other person will get the same permission from the same application; that applies also to co-maintainers/maintainers of the project used for the application.
• We only accept an application per user. If you change your mind about the project to use for this application, or it is necessary to use a different project for the application, please update the issue summary with the link to the correct project and the issue title with the project name and the branch to review.

To the reviewers

Please read How to review security advisory coverage applications, Application workflow, What to cover in an application review, and Tools to use for reviews.

The important notes are the following.

• It is preferable to wait for a project moderator before posting the first comment on newly created applications. Project moderators will do some preliminary checks that are necessary before any change on the project files is suggested.
• Reviewers should show the output of a CLI tool only once per application.
• It may be best to have the applicant fix things before further review.

For new reviewers, I would also suggest to first read In which way the issue queue for coverage applications is different from other project queues.

1. FILE: image_404_fallback.info.yml

package: 'Custom'

Custom is not a package value used for projects hosted on drupal.org. That is not a mandatory value, and it can be omitted.

2. FILE: image_404_fallback.module

For a new module that aims to be compatible with Drupal 10 and Drupal 11, I would rather implement hooks as class methods as described in Support for object oriented hook implementations using autowired services.
It would require increasing the minimum Drupal 10 version supported, but Drupal 10.1 is no longer supported.

3. FILE: src/EventSubscriber/Image404Subscriber.php

  /**
   * The file system service.
   *
   * @var \Drupal\Core\File\FileSystemInterface
   */
  protected FileSystemInterface $fileSystem;

  /**
   * The config factory.
   *
   * @var \Drupal\Core\Config\ConfigFactoryInterface
   */
  protected ConfigFactoryInterface $configFactory;

  /**
   * The logger factory.
   *
   * @var \Drupal\Core\Logger\LoggerChannelFactoryInterface
   */
  protected LoggerChannelFactoryInterface $loggerFactory;

  /**
   * Constructs an Image404Subscriber.
   *
   * @param \Drupal\Core\File\FileSystemInterface $file_system
   *   The file system service.
   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $logger_factory
   *   The logger factory service.
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The config factory service.
   */
  public function __construct(FileSystemInterface $file_system, LoggerChannelFactoryInterface $logger_factory, ConfigFactoryInterface $config_factory) {
    $this->fileSystem = $file_system;
    $this->loggerFactory = $logger_factory;
    $this->configFactory = $config_factory;
  }

New modules, which are compatible with Drupal 10 and higher versions are expected to use constructor property promotion.

4. FILE: src/Form/Image404FallbackSettingsForm.php

With Drupal 10 and Drupal 11, there is no longer need to use #default_value for each form element, when the parent class is ConfigFormBase: It is sufficient to use #config_target, as in the following code.

    $form['image_toolkit'] = [
      '#type' => 'radios',
      '#title' => $this->t('Select an image processing toolkit'),
      '#config_target' => 'system.image:toolkit',
      '#options' => [],
    ];

Using that code, it is no longer needed to save the configuration values in the form submission handler: The parent class will take care of that.
For this change, it is necessary to require at least Drupal 10.3, but that is not an issue, since Drupal 10.2.x is no longer supported.

As a side note: These applications do not require that new releases are created after reviews.

Rest seems fine to me.

Please wait for other reviewers and Project Moderator to take a look and if everything goes fine, you will get the role.