[BUGFIX] Fix structure of generated finisher FlexForm fields

A valid FlexForm field must have a "TCEforms" wrapper around
the field configuration as can be seen in the FlexFormTools
class.

Resolves: #88013
Releases: master
Change-Id: I986f4fdf6f32c7174b3967f75729bc1122d4fdbd
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60607


Tested-by: Dominik Merkel <merkel.dominik@googlemail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Dominik Merkel <merkel.dominik@googlemail.com>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>

typo3/sysext/form/Classes/Domain/Configuration/FlexformConfiguration/Processors/FinisherOptionGenerator.php

@@ -95,7 +95,7 @@ class FinisherOptionGenerator extends AbstractProcessor
         $elementConfiguration['config']['default'] = $optionValue;
 
         $sheetElements = $this->converterDto->getResult();
-        $sheetElements['settings.finishers.' . $finisherIdentifier . '.' . $optionKey] = $elementConfiguration;
+        $sheetElements['settings.finishers.' . $finisherIdentifier . '.' . $optionKey]['TCEforms'] = $elementConfiguration;
 
         $this->converterDto->setResult($sheetElements);
     }