Quite some work done here.

src/Tech/Controller/ActivationController.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace App\Tech\Controller;
+
+use App\Tech\Repository\UserRepository;
+use App\Tech\Service\EmailVerifier;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Annotation\Route;
+use SymfonyCasts\Bundle\VerifyEmail\Exception\VerifyEmailExceptionInterface;
+
+class ActivationController extends AbstractController
+{
+    #[Route('/verify/email', name: 'app_verify_email')]
+    public function verifyUserEmail(Request $request, UserRepository $userRepository, EmailVerifier $emailVerifier): Response
+    {
+        $id = $request->query->get('id');
+
+        if (null === $id) {
+            return $this->redirectToRoute('app_register');
+        }
+
+        $user = $userRepository->find($id);
+
+        if (null === $user) {
+            return $this->redirectToRoute('app_register');
+        }
+
+        // validate email confirmation link, sets User::isVerified=true and persists
+        try {
+            $emailVerifier->handleEmailConfirmation($request, $user);
+        } catch (VerifyEmailExceptionInterface $exception) {
+            $this->addFlash('error', $exception->getReason());
+
+            return $this->redirectToRoute('app_register');
+        }
+
+        $this->addFlash('success', 'Your email address has been verified. You can now log in.');
+
+        return $this->redirectToRoute('app_login');
+    }
+}