Which StorageDefinition (FieldType) for multiple entity autocomplete field?

Hi,

I need to know, which type of storage definition I have to use, when i have an entity reference field.

My code: (Focus on “tags”)

FieldType Definition:

    public static function propertyDefinitions(StorageDefinition $storage) {

        $properties = [];

        $properties['quantity'] = DataDefinition::create('string')->setLabel(t('Quantity'));

        $properties['style'] = DataDefinition::create('string')->setLabel(t('Style'));
        
        //$properties['tags'] = DataReferenceDefinition::create('entity')->setLabel(t('Tags'));
        //$properties['tags'] = MapDataDefinition::create()->setLabel(t('Tags'));
        $properties['tags'] = DataDefinition::create('entity_reference')->setLabel(t('Tags'));

        return $properties;
    }

    public static function schema(StorageDefinition $storage) {

        $columns = [];
        $columns['quantity'] = [
            'type' => 'int',
            'length' => 3,
        ];
        $columns['style'] = [
            'type' => 'varchar',
            'length' => '255',
        ];
        $columns['tags'] = [
            'type' => 'varchar',
            'length' => '255',
        ];

        return [
            'columns' => $columns,
            'indexes' => [],
        ];
    }

FieldWidget Definition:

    public function formElement(
        FieldItemListInterface $items,
        $delta, 
        Array $element, 
        Array &$form, 
        FormStateInterface $formState
    ) {

        $element['quantity'] = [
            '#type' => 'number',
            '#title' => t('Quantity'),
            '#default_value' => isset($items[$delta]->quantity) ? $items[$delta]->quantity : null,
            '#size' => 3,
        ];
        
        $element['style'] = [
            '#type' => 'select',
            '#title' => t('Style'),
            '#options' => array(
                [...]
            ),
            '#default_value' => isset($items[$delta]->style) ? $items[$delta]->style : null,
        ];
        
        $element['tags'] = [
            '#type' => 'entity_autocomplete',
            '#target_type' => 'taxonomy_term',
            '#title' => t('Tags'),
            '#tags' => TRUE,
            '#selection_settings' => [
                'include_anonymous' => FALSE,
            ],
        ];
        return $element;
    }
Drupal version: 


Source: https://www.drupal.org/taxonomy/term/4/feed