Laravel Create Product Order Api

I'm building an API for e-commerce app

now, i get stuck in creating order

i have the following Migrations

Orders

        Schema::create('orders', function (Blueprint $table) {
        $table->id();
        $table->string('order_number');
        $table->unsignedBigInteger('user_id');
        $table->enum('status', ['pending','processing','completed','decline'])->default('pending');
        $table->float('grand_total');
        $table->integer('item_count');
        $table->boolean('is_paid')->default(false);
        $table->enum('payment_method', ['cash_on_delivery'])->default('cash_on_delivery');
        $table->string('notes')->nullable();

        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
        $table->timestamps();
    });

Order_items

        Schema::create('order_items', function (Blueprint $table) {
        $table->id();
        $table->unsignedBigInteger('order_id');
        $table->unsignedBigInteger('product_id');

        $table->foreign('product_id')->references('id')->on('products')->onDelete('cascade');
        $table->foreign('order_id')->references('id')->on('orders')->onDelete('cascade');

        $table->float('price');
        $table->integer('quantity');

        $table->timestamps();
    });

Products

Schema::create('products', function (Blueprint $table) {
        $table->increments('id');
        $table->string('img');
        $table->string('name');
        $table->string('desc');
        $table->integer('price');
        $table->timestamps();
    });

and this is Models Relationship

Order Model

public function items()
{
    return $this->belongsToMany(Medicine::class, 'order_item','order_id','product_id')->withPivot('quantity','price');
}

public function user()
{
    return $this->belongsTo(User::class);
}

Controller

    public function store(Request $request)
{

    $order = new Order();
    $order->order_number = uniqid('ORD.');
    $order->user_id = 1;
    $order->item_count = 2;
    $order->grand_total = 20;
    $order->save();

            $items = $request->json()->all();
        foreach( $items as $item ){
            $orderItem = new OrderItem();
            $orderItem->order_id = $order->id;
            $orderItem->product_id = $item['product_id'];
            $orderItem->price = $item['price'];
            $orderItem->quantity = $item['quantity'];
            $orderItem->save();
        }

    return response(['message'=>'successful']);
}

Now, i can add Orders successfully .

but how to add items from JSON Request

for example by posting JSON Data from Postman

JSON Post Request

    [
    {
        "id":1,
        "product_id":4018,
     "price":20,
     "quantity":1
    },
    {
        "id":2,
        "product_id":4019,
     "price":50,
     "quantity":3
    },
    {
        "id":3,
        "product_id":4020,
     "price":45,
     "quantity":2
    }
]

any ideas?

Update

Photo of Post Request

via Chebli Mohamed