add notes/remark and refactor round-trip

app-modules/payment/src/Models/Refund.php

@@ -6,6 +6,7 @@ use App\Models\User;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Modules\Booking\Models\Booking;
 use Modules\Payment\Database\Factories\RefundFactory;
 use Modules\Payment\Enums\RefundStatus;
 use Spatie\Activitylog\Models\Concerns\LogsActivity;
@@ -38,6 +39,7 @@ class Refund extends Model
      */
     protected $fillable = [
         'payment_id',
+        'booking_id',
         'status',
         'amount',
         'reason',
@@ -67,6 +69,16 @@ class Refund extends Model
         return $this->belongsTo(Payment::class);
     }
 
+    /**
+     * The leg actually being refunded/cancelled — not necessarily
+     * payment->booking, since a round trip's return leg refunds against the
+     * primary leg's shared Payment (domain.md §2b).
+     */
+    public function booking(): BelongsTo
+    {
+        return $this->belongsTo(Booking::class);
+    }
+
     public function requestedBy(): BelongsTo
     {
         return $this->belongsTo(User::class, 'requested_by');