add upload invoice and test

database/migrations/2018_06_21_040652_create_invoice_table.php

@@ -0,0 +1,35 @@
+<?php
+
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class CreateInvoiceTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('invoices', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('invoice_url');
+            $table->double('amount');
+            $table->integer('booking_id')->unsigned();
+            $table->foreign('booking_id')->references('id')->on('bookings');
+            $table->timestamps();
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::dropIfExists('invoices');
+    }
+}