feat(Inventory): update add method

src/bookstore/inventory.py

@@ -29,8 +29,9 @@ class Inventory:
         """Close database connection."""
         self.conn.close()
 
-    def add(self, book: Book) -> None:
+    def add(self, *books: list[Book]) -> None:
         """Add `Book` to the `Inventory`. `Book`s ISBN must be unique."""
+        for book in books:
             try:
                 self.cursor.execute("INSERT INTO Book VALUES (?, ?, ?, ?, ?)", (book.isbn, book.title, book.author, book.price, book.stock))
                 self.conn.commit()