[FEATURE] Add "forField" as view variable when extracting form

Allows templates to make conditions etc. on the current
TCA field context. Useful for page templates which have
two TCA fields with Flux forms as DS.

Classes/Provider/AbstractProvider.php

@@ -177,7 +177,8 @@ protected function getViewVariables(array $row, ?string $forField = null): array
         $fieldName = $forField ?? $this->getFieldName($row);
         $variables = [
             'record' => $row,
-            'settings' => $this->typoScriptService->getSettingsForExtensionName($extensionKey)
+            'settings' => $this->typoScriptService->getSettingsForExtensionName($extensionKey),
+            'forField' => $forField,
         ];
 
         // Special case: when saving a new record variable $row[$fieldName] is already an array

Tests/Unit/Content/RuntimeDefinedContentProviderTest.php

@@ -179,6 +179,7 @@ public function testGetTemplateVariables(): void
         $expected = [
             'record' => $record,
             'settings' => [],
+            'forField' => null,
             'page' => [],
             'user' => [],
             'contentType' => $this->contentTypeDefinition,