Feature: #107712 - Introduce card-based submodule overview

Description

Backend modules can now display a card-based overview of their submodules instead of automatically redirecting to the first available submodule. This new showSubmoduleOverview configuration option enables a more user-friendly navigation experience, similar to the Install Tool's maintenance card layout.

When enabled, clicking on a second-level module displays an overview page with cards for each accessible submodule. Each card shows the module's icon, title, description, and an "Open module" button, allowing users to make an informed choice about which submodule to access.

Example configuration

return [
    'web_info' => [
        'parent' => 'content',
        'showSubmoduleOverview' => true,
        // ...
    ],
    'web_info_overview' => [
        'parent' => 'web_info',
        'access' => 'user',
        'path' => '/module/web/info/overview',
        'iconIdentifier' => 'module-info',
        'labels' => 'info.modules.overview',
        // ... routes and other configuration
    ],
    'web_info_translations' => [
        'parent' => 'web_info',
        'access' => 'user',
        'path' => '/module/web/info/translations',
        'iconIdentifier' => 'module-info',
        'labels' => 'info.modules.translations',
        // ... routes and other configuration
    ],
];

In this example, the Content > Status module displays a card-based overview showing both Pagetree Overview and Localization Overview submodules. Users can read the description of each module before deciding which one to open.

The feature works seamlessly with the existing module permission system. Only submodules that the current user has access to are displayed in the overview. If no accessible submodules exist, a helpful information message is shown instead of an empty page.

Note

The "Content > Status" was called "Web > Info" before TYPO3 v14, see also Feature: #107628 - Improved backend module naming and structure.

Implementation details

The showSubmoduleOverview option modifies the behavior in several key areas:

Module routing - When set to true, the module's default route targets SubmoduleOverviewController instead of automatically redirecting to the first available submodule.
Middleware behavior - The BackendModuleValidator middleware skips its automatic submodule redirection logic when this option is enabled, allowing the overview page to be displayed.
Navigation enhancement - The system provides automatic navigation capabilities:
- The SubmoduleOverviewController displays the submodule jump menu, allowing quick access to all available submodules.
- When showSubmoduleOverview is activated, the ModuleTemplate automatically adds a "Module Overview" menu item to the submodule dropdown.
- This allows users to easily navigate back to the overview from any submodule, especially useful when a submodule does not manually provide a "go back" button.

To provide meaningful descriptions on the overview cards, modules should define a description or shortDescription in their labels configuration. These are displayed in the card body to help users understand each submodule's purpose.

Impact

Backend navigation becomes more intuitive and self-documenting. Container modules using showSubmoduleOverview provide users with a clear overview of available functionality, eliminating the confusion of being automatically redirected to an arbitrary first submodule.

The Content > Status module now uses this feature to present its submodules in an accessible, visually organized manner. Users can quickly understand what each submodule offers before navigating to it, improving discoverability and user experience in the TYPO3 backend.