In my custom extensions’ TCA I am updating FAL reference fields to work with TYPO3 v12/v13. Previously I had defined a fieldname which was a camelCase version of the TCA/SQL fieldname (imgRel for img_rel: first argument of getFileFieldTCAConfig()) This camelCase value is now stored under sys_file_reference.fieldname – but TYPO3v12 searches for img_rel and therefore does not show referenced files.

Question: How can I get this fieldname into the configuration for the TCA type file?

Example of a configuration for TYPO3 < 12:

'img_rel' => [
    'label' => 'Image',
    'config' => TYPO3CMSCoreUtilityExtensionManagementUtility::getFileFieldTCAConfig(
        'imgRel',
        ['maxitems' => 1],
        $GLOBALS['TYPO3_CONF_VARS']['GFX']['imagefile_ext']
    ),
],

Same example as above for TYPO3 >= 12:

I cannot find a fieldname property or anything similar in the documentation.

'img_rel' => [
    'label' => 'Image',
    'config' => [
        'type' => 'file',
        'maxitems' => 1,
        'allowed' => 'common-image-types',
    ]
],