add services && controller && first configuration tree builder

BillingBundle/DependencyInjection/Configuration.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Acme\SocialBundle\DependencyInjection;
+
+use Symfony\Component\Config\Definition\Builder\TreeBuilder;
+use Symfony\Component\Config\Definition\ConfigurationInterface;
+
+class Configuration implements ConfigurationInterface
+{
+    public function getConfigTreeBuilder()
+    {
+        $treeBuilder = new TreeBuilder('billing');
+
+        $treeBuilder->getRootNode()->children()
+            ->arrayNode('stripe')->children()
+                ->scalarNode('stripe_api_key_pub')->end()
+                ->scalarNode('stripe_api_key')->end()
+                ->scalarNode('stripe_webhook_key')->end()
+            ->end()
+        ->end();
+
+
+        return $treeBuilder;
+    }
+}