fix: flow on scan + owners managment

lib/domain/models/book_instance.dart

@@ -0,0 +1,28 @@
+class BookInstance {
+  BookInstance({
+    required this.balId,
+    required this.bookId,
+    required this.id,
+    required this.ownerId,
+    required this.price,
+    required this.status,
+    this.soldPrice,
+  });
+
+  int balId;
+  int bookId;
+  int id;
+  int ownerId;
+  double price;
+  double? soldPrice;
+  bool status;
+
+  factory BookInstance.fromJSON(Map<String, dynamic> json) => BookInstance(
+    balId: json["balId"],
+    bookId: json["bookId"],
+    id: json["id"],
+    ownerId: json["ownerId"],
+    price: json["price"],
+    status: json["status"],
+  );
+}