Feature #91859: Allow SelectCheckBox groups to be initally expanded

See Issue #91859

Description

A new TCA setting expandAll has been added to FormEngine type select with renderType selectCheckBox. It allows to define the initial display behavior for grouped checkboxes.

By adding the new setting 'expandAll' => true, all select groups are initially expanded.

Please note, that the new setting is placed in ['config']['appearance'] and is not a top level configuration key. Therefore the full path is: $GLOBALS['TCA'][$table]['columns'][$field]['config']['appearance']['expandAll']

Example

'select_checkbox' => [
    'label' => 'select_checkbox - expandAll',
    'config' => [
        'type' => 'select',
        'renderType' => 'selectCheckBox',
        'appearance' => [
            'expandAll' => true
        ],
        'items' => [
            ['group 1', '--div--'],
            ['check 1', 1],
            ['check 2', 2],
            ['check 3', 3],
            ['group 2', '--div--'],
            ['check 4', 4],
            ['check 5', 5]
        ]
    ]
]

Impact

It’s now possible to initally expand all checkbox groups. Integrators can therefore provide their editors with all the choices at once, without having to open each select group individually. The possibility to close each group remains unchanged for the editor.