feat: forms on TYPO3 13, loaded into the static pages with htmx

The static export replaced every EXT:form form with a contact notice. The
forms are back, rendered by TYPO3 13 and embedded in the static pages:

- Page type 1704 (/<page>/form) renders only the form plugin of a page,
  inside a .form-island element. Every form posts to that URL
  (renderingOptions.additionalParams), because on www the page URL is a
  static file that never reaches TYPO3. htmx swaps the island in place:
  validation errors, multi-step pages and confirmations. A redirect to an
  htmx request becomes HX-Redirect (HtmxRedirectMiddleware), so Redirect
  finishers send the browser to the thank-you page.
- While a request runs, an overlay with a spinner (as in MyE&P) covers
  the form. Styled inside the island: the static pages load the CSS of
  the TYPO3 10 export.
- The bw_captcha image comes from /<page>/captcha for the same reason.
  Both suffixes are in the PageType enhancer of every site with forms
  (semesterende gets one with default '' to keep its URLs).
- Ported from TYPO3 10: form setup, templates and partials, the MyE&P
  address finisher, the job application finisher with the MyE&P Team
  API client (epTeamApi* in secrets.php), the page URL/referrer finisher
  with ReferrerMiddleware (?ref=), the e-mail layout without the system
  footer, bw_captcha 5 and form_element_linked_checkbox 6. The address
  check forms are dropped.
- German language packs (EXT:form messages): availableLanguages = de,
  fetched on every deploy (typo3:language:update).
- The checkbox partials passed null to VHS' substring, which PHP 8.5
  reports as deprecated.
- DDEV no longer turns deprecations into exceptions, matching
  production: EXT:form's RenderFormValueViewHelper uses null as an array
  offset for empty optional fields (core bug, also in 13.4.37).

The static pages get their placeholders from the exporter in EP/website,
see .ddev/plans/static-export-form-islands.patch (local only).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/ep_theme/Classes/Form/AddReferrerFinisher.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace EP\EpTheme\Form;
+
+use EP\EpTheme\Middleware\ReferrerMiddleware;
+use TYPO3\CMS\Core\Routing\PageArguments;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\CMS\Form\Domain\Finishers\AbstractFinisher;
+use TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication;
+
+/**
+ * Adds the URL of the form's page and, if known, the page the visitor came from (see
+ * ReferrerMiddleware) to the submission, so the e-mail finishers include them.
+ */
+class AddReferrerFinisher extends AbstractFinisher
+{
+    protected function executeInternal()
+    {
+        $this->addCurrentUrlField();
+        $this->addReferrerField();
+    }
+
+    private function addReferrerField(): void
+    {
+        $frontendUser = $this->finisherContext->getRequest()->getAttribute('frontend.user');
+        if (!$frontendUser instanceof FrontendUserAuthentication) {
+            return;
+        }
+
+        $referrer = $frontendUser->getKey('ses', ReferrerMiddleware::SESSION_KEY);
+        if (null === $referrer) {
+            return;
+        }
+
+        $this->addField('referrer', 'Referrer', $referrer);
+
+        $frontendUser->setKey('ses', ReferrerMiddleware::SESSION_KEY, null);
+        $frontendUser->storeSessionData();
+    }
+
+    private function addCurrentUrlField(): void
+    {
+        $request = $this->finisherContext->getRequest();
+        $routing = $request->getAttribute('routing');
+        $site = $request->getAttribute('site');
+        if (!$routing instanceof PageArguments || !$site instanceof Site) {
+            return;
+        }
+
+        // The page itself, not the form page type the submission was posted to
+        $url = (string)$site->getRouter()->generateUri($routing->getPageId(), [
+            '_language' => $request->getAttribute('language'),
+        ]);
+        $this->addField('pageurl', 'URL', $url);
+    }
+
+    private function addField(string $identifier, string $label, string $value): void
+    {
+        $field = $this->finisherContext
+            ->getFormRuntime()
+            ->getFormDefinition()
+            ->getPageByIndex(0)
+            ->createElement($identifier, 'Text');
+
+        $field->setDefaultValue($value);
+        $field->setDataType('string');
+        $field->setLabel($label);
+
+        // Finisher variable for potential later use
+        $this->finisherContext->getFinisherVariableProvider()->add(
+            $this->shortFinisherIdentifier,
+            $identifier,
+            $value
+        );
+    }
+}