Add support for Key Auth

Plugin plus configuration support to allows users to pass a key that
will be used in requests.

src/DMS/Service/Meetup/ClientFactory.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace DMS\Service\Meetup;
+
+use DMS\Service\Meetup\Config\ClientConfig;
+use Guzzle\Service\Loader\JsonLoader;
+use GuzzleHttp\Client as GuzzleClient;
+use GuzzleHttp\Command\Guzzle\Description;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Middleware;
+use Symfony\Component\Config\FileLocator;
+
+final class ClientFactory
+{
+    private const DESCRIPTION_PATH = __DIR__ . '/../../../../description';
+
+    public static function buildClient(ClientConfig $config)
+    {
+
+        $default = [
+            'base_uri' => 'http://api.meetup.com/',
+        ];
+
+        $locator    = new FileLocator([self::DESCRIPTION_PATH]);
+        $jsonLoader = new JsonLoader($locator);
+
+        $description = $jsonLoader->load($locator->locate('meetup.json'));
+        $description = new Description($description);
+
+        $stack = HandlerStack::create();
+
+        foreach ($config->getMiddleware() as $name => $middleware) {
+            $stack->push(Middleware::mapRequest($middleware), $name);
+        }
+
+        $config = array_merge($default, [
+            'handler' => $stack
+        ]);
+
+        $client = new GuzzleClient($config);
+
+
+        return new Client($client, $description);
+    }
+}

src/DMS/Service/Meetup/Config/ClientConfig.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace DMS\Service\Meetup\Config;
+
+interface ClientConfig
+{
+    /**
+     * @return callable[]
+     */
+    public function getMiddleware(): array;
+}

src/DMS/Service/Meetup/Config/KeyAuthConfig.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace DMS\Service\Meetup\Config;
+
+use DMS\Service\Meetup\Plugin\KeyAuthPlugin;
+
+final class KeyAuthConfig implements ClientConfig
+{
+    /**
+     * @var string
+     */
+    protected $key;
+
+    /**
+     * @param string $key
+     */
+    public function __construct($key)
+    {
+        $this->key = $key;
+    }
+
+    public function getMiddleware(): array
+    {
+        return [
+            'add key' => new KeyAuthPlugin($this->key)
+        ];
+    }
+
+}

src/DMS/Service/Meetup/Plugin/KeyAuthPlugin.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace DMS\Service\Meetup\Plugin;
+
+use Psr\Http\Message\RequestInterface;
+
+final class KeyAuthPlugin
+{
+    /**
+     * @var string
+     */
+    protected $key;
+
+    public function __construct(string $key)
+    {
+        $this->key = $key;
+    }
+
+    public function __invoke(RequestInterface $request): RequestInterface
+    {
+        $uri = $request->getUri();
+        $uri = $uri->withQuery($uri->getQuery() . '&key=' . $this->key);
+
+        return $request->withUri($uri);
+    }
+}