feat: move prepopulation guards into participant service

src/Controller/Booking/Create/Step2Controller.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Controller\Booking\Create;
 
+use App\Entity\User;
 use App\Controller\Booking\Traits\BookingCreateTrait;
 use App\Controller\Booking\Traits\BookingExceptionHandlerTrait;
 use App\Form\BookingCreateStep2Type;
@@ -65,12 +66,18 @@ class Step2Controller extends AbstractController
         // Enrich with fresh availability data
         $this->travelDataService->enrichWithFreshAvailabilities($bookingCreateDto->travel);
 
-        // Ensure correct number of participants with prepopulation callback
-        $this->participantCountService->ensureCorrectNumberOfParticipants(
-            $bookingCreateDto,
-            $this->getUser(),
-            fn ($user, $participant) => $this->prepopulationService->prepopulateApplicantFromUser($user, $participant)
-        );
+        // Ensure correct number of participants first, then prepopulate the applicant if needed.
+        $this->participantCountService->ensureCorrectNumberOfParticipants($bookingCreateDto);
+
+        $user = $this->getUser();
+        if ($user instanceof User
+            && isset($bookingCreateDto->participants[0])
+            && $this->prepopulationService->shouldPrepopulateApplicant($bookingCreateDto->participants[0])) {
+            $bookingCreateDto->participants[0] = $this->prepopulationService->prepopulateApplicantFromUser(
+                $user,
+                $bookingCreateDto->participants[0]
+            );
+        }
 
         // Validate room assignments against current selection (handles back-navigation from step 2 to step 1)
         $this->roomAssignmentService->validateAndResetInvalidAssignments($bookingCreateDto);