feat: add a CAS Authentication Entry Point

This let people gets redirected to the page where they comes from once they are authenticated.

(cherry picked from commit 173dc52)

src/Security/CasAuthenticationEntryPoint.php

@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ *
+ * @see https://github.com/ecphp
+ */
+
+declare(strict_types=1);
+
+namespace EcPhp\CasBundle\Security;
+
+use Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Component\Security\Http\EntryPoint\AuthenticationEntryPointInterface;
+
+final class CasAuthenticationEntryPoint extends AuthenticationEntryPointInterface
+{
+    private UrlGeneratorInterface $urlGenerator;
+
+    public function __construct(UrlGeneratorInterface $urlGenerator)
+    {
+        $this->urlGenerator = $urlGenerator;
+    }
+
+    public function start(Request $request, AuthenticationException $authException = null): RedirectResponse
+    {
+        return new RedirectResponse(
+            $this
+                ->urlGenerator
+                ->generate(
+                    'cas_bundle_login',
+                    $request->query->all() + ['service' => $request->getUri()],
+                );
+            );
+
+    }
+}