feat: reduce session payload

src/Form/Model/BookingDto.php

@@ -325,4 +325,62 @@ class BookingDto
     {
         return AgencyLoader::INTERNAL_AGENCY_CODE === $this->agencyCode;
     }
+
+    /**
+     * Controls session serialization to exclude the heavy Travel object graph.
+     *
+     * Replaces the full Travel object with just its integer ID. The Booking's
+     * travelData reference is also removed since it points to the same object.
+     * BookingService::hydrate() restores the Travel from cache after session read.
+     *
+     * @return array<string, mixed>
+     */
+    public function __serialize(): array
+    {
+        $data = get_object_vars($this);
+
+        // Replace the full Travel object graph with just its ID
+        $data['travel'] = $this->travel->id;
+
+        // Clone Booking to avoid mutating the live object, then strip its
+        // travelData reference which points to the same heavy Travel graph
+        if (null !== $this->booking) {
+            $booking = clone $this->booking;
+            $booking->travelData = null;
+            $data['booking'] = $booking;
+        }
+
+        return $data;
+    }
+
+    /**
+     * Restores the DTO from session data with a minimal Travel placeholder.
+     *
+     * Creates a Travel object containing only the ID. BookingService::hydrate()
+     * replaces this with the full Travel from cache on every session read.
+     *
+     * @param array<string, mixed> $data
+     */
+    public function __unserialize(array $data): void
+    {
+        // Extract the travel ID before the property loop — 'travel' in the
+        // serialized data is an int, not a Travel object
+        $travelId = $data['travel'];
+        unset($data['travel']);
+
+        // Skip keys that no longer exist as declared properties to avoid
+        // dynamic property creation (deprecated since PHP 8.2)
+        foreach ($data as $key => $value) {
+            if (false === property_exists($this, $key)) {
+                continue;
+            }
+            $this->$key = $value;
+        }
+
+        // Create a skeleton Travel with only the ID; BookingService::hydrate()
+        // replaces this with the full object from cache
+        $travel = new Travel();
+        $travel->id = $travelId;
+        $this->travel = $travel;
+    }
 }