Transforming into a composer package class

As I should use this into more than one project, it would be better to
turn it into a composer package. So I learn how to do that and use it at
work at the same time.

src/oauth.php

@@ -0,0 +1,41 @@
+<?php
+/**
+ * A very compact and simple Memsource API library
+ * 
+ * @author Bruno Fontes <developer@brunofontes.net>
+ * @link   https://github.com/brunofontes
+ */
+namespace BrunoFontes\Memsource;
+
+class Oauth extends \BrunoFontes\Memsource
+{
+    private $_url = '/oauth';
+    
+    /**
+     * Get the URL to generate the Authorization Code from Memsource
+     *
+     * @param string $client_id     Memsource client ID
+     * @param string $client_secret Memsource client secret
+     * @param string $callback_uri  URL that Memsource will redirect to
+     * 
+     * @return string the authorization code
+     */
+    public function getAuthorizationCodeUrl(string $client_id, string $callback_uri)
+    {
+        $authorize_url = $this->_url . '/authorize';
+        return $authorize_url . '?response_type=code&client_id=' . $client_id . '&redirect_uri=' . $callback_uri . '&scope=openid';
+    }
+
+    public function getAccessToken(string $authorization_code, string $client_id, string $client_secret, string $callback_uri)
+    {
+        $token_url = $this->_url . '/token';
+        $authorization = base64_encode("$client_id:$client_secret");
+        $header = ["Authorization: Basic {$authorization}", 'Content-Type: application/x-www-form-urlencoded'];
+        $content = "grant_type=authorization_code&code=$authorization_code&redirect_uri=$callback_uri";
+        $response = $this->post($token_url, $content, [], $header);
+        if ($respose['error']) {
+            throw new Exception("Error getting access token", 1);
+        }
+        return $response['access_token'];
+    }
+}