Add Cart model, resource and its API, Pivot table with Items.

Update Items model to have relationship with cart.

app/Http/Controllers/API/v2/CartController.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace App\Http\Controllers\API\v2;
+
+use App\Http\Requests\StoreCartRequest;
+use App\Http\Requests\UpdateCartRequest;
+use App\Http\Resources\API\v2\CartResource;
+use App\Models\Cart;
+
+class CartController extends Controller
+{
+    /**
+     * Display a listing of the resource.
+     */
+    public function index()
+    {
+        //
+    }
+
+    /**
+     * Show the form for creating a new resource.
+     */
+    public function create()
+    {
+        //
+    }
+
+    /**
+     * Store a newly created resource in storage.
+     */
+    public function store(StoreCartRequest $request)
+    {
+        //
+    }
+
+    /**
+     * Display the specified resource.
+     */
+    public function show(Cart $cart)
+    {
+        return new CartResource($cart);
+    }
+
+    /**
+     * Show the form for editing the specified resource.
+     */
+    public function edit(Cart $cart)
+    {
+        //
+    }
+
+    /**
+     * Update the specified resource in storage.
+     */
+    public function update(UpdateCartRequest $request, Cart $cart)
+    {
+        //
+    }
+
+    /**
+     * Remove the specified resource from storage.
+     */
+    public function destroy(Cart $cart)
+    {
+        //
+    }
+}