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/Middleware/ReferrerMiddleware.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace EP\EpTheme\Middleware;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use TYPO3\CMS\Core\Exception\SiteNotFoundException;
+use TYPO3\CMS\Core\Site\SiteFinder;
+use TYPO3\CMS\Frontend\Authentication\FrontendUserAuthentication;
+
+/**
+ * Links to a form page carry the uid of the page they come from (?ref=123, e.g. the enquiry
+ * button of a product page). Its URL is kept in the session until AddReferrerFinisher puts it
+ * into the submission. On static pages the parameter reaches TYPO3 with the request that loads
+ * the form (see the form placeholder of the static export).
+ */
+class ReferrerMiddleware implements MiddlewareInterface
+{
+    public const SESSION_KEY = 'referrer';
+
+    public function __construct(private readonly SiteFinder $siteFinder) {}
+
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $ref = $request->getQueryParams()['ref'] ?? null;
+        $frontendUser = $request->getAttribute('frontend.user');
+
+        if (!is_numeric($ref) || !$frontendUser instanceof FrontendUserAuthentication) {
+            return $handler->handle($request);
+        }
+
+        try {
+            $url = (string)$this->siteFinder->getSiteByPageId((int)$ref)->getRouter()->generateUri((int)$ref);
+            $frontendUser->setKey('ses', self::SESSION_KEY, $url);
+            $frontendUser->storeSessionData();
+        } catch (SiteNotFoundException) {
+        }
+
+        return $handler->handle($request);
+    }
+}