Cron: Support KS/UI forms

With this commit cron job implementations
are allowed to migrate from legacy forms
to the UI/KS forms.

An instance of `ilCronJob` can provide a
boolean `false` when overriding `usesLegacyForms`
and then simply provide own implementations of
`getCustomConfigurationSections` and
`saveCustomConfiguration`.

components/ILIAS/Cron/classes/class.ilCronJob.php

@@ -248,10 +248,45 @@ public function hasCustomSettings(): bool
         return false;
     }
 
+    /**
+     * @deprecated
+     */
+    #[\Deprecated('Will be removed without any alternative, KS/UI forms will be expected', since: '13.0')]
+    public function usesLegacyForms(): bool
+    {
+        return true;
+    }
+
+    /**
+     * @return array<string, \ILIAS\UI\Component\Input\Field\Section> A map of sections to be added to the configuratio form
+     */
+    public function getCustomConfigurationSections(
+        \ILIAS\UI\Factory $ui_factory,
+        \ILIAS\Refinery\Factory $factory,
+        ilLanguage $lng
+    ): array {
+        return [];
+    }
+
+    /**
+     * @deprecated
+     */
+    #[\Deprecated('Will be removed without any alternative, KS/UI forms will be expected', since: '13.0')]
     public function addCustomSettingsToForm(ilPropertyFormGUI $a_form): void
     {
     }
 
+    /**
+     * @param array<string, mixed> $group_data data of the that group as array, as processed by the KS
+     */
+    public function saveCustomConfiguration(array $form_data): void
+    {
+    }
+
+    /**
+     * @deprecated
+     */
+    #[\Deprecated('Will be removed without any alternative, KS/UI forms will be expected', since: '13.0')]
     public function saveCustomSettings(ilPropertyFormGUI $a_form): bool
     {
         return true;