feat: unique email addresses of participants unless child, cleanup

addresses #869axbn21

src/Form/Model/BookingDto.php

@@ -195,4 +195,44 @@ class BookingDto
                 ->addViolation();
         }
     }
+
+    #[Assert\Callback(groups: ['booking_create_step_2', 'booking_edit'])]
+    public function validateEmailUniqueness(ExecutionContextInterface $context): void
+    {
+        // Build map of email addresses to participant indices (adults only)
+        $emailMap = [];
+
+        foreach ($this->participants as $index => $participant) {
+            // Skip children (they can share email addresses)
+            if (true === $participant->isChild()) {
+                continue;
+            }
+
+            // Skip null or empty emails (handled by other validators)
+            if (null === $participant->email || '' === trim($participant->email)) {
+                continue;
+            }
+
+            // Normalize email for case-insensitive comparison
+            $normalizedEmail = strtolower(trim($participant->email));
+
+            // Add participant index to the email map
+            if (false === isset($emailMap[$normalizedEmail])) {
+                $emailMap[$normalizedEmail] = [];
+            }
+            $emailMap[$normalizedEmail][] = $index;
+        }
+
+        // Add validation errors for duplicate emails
+        foreach ($emailMap as $email => $indices) {
+            // Only add violations if email is used by multiple adult participants
+            if (1 < count($indices)) {
+                foreach ($indices as $index) {
+                    $context->buildViolation('Diese E-Mail Adresse wird bereits von einem anderen erwachsenen Teilnehmer verwendet')
+                        ->atPath(sprintf('participants[%d].email', $index))
+                        ->addViolation();
+                }
+            }
+        }
+    }
 }