Add oauth token method

tests/GhostZero/BitinflowAccounts/ApiOauthTest.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GhostZero\BitinflowAccounts\Tests;
+
+use GhostZero\BitinflowAccounts\Tests\TestCases\ApiTestCase;
+
+/**
+ * @author René Preuß <rene@preuss.io>
+ */
+class ApiOauthTest extends ApiTestCase
+{
+
+    public function testGetOauthToken(): void
+    {
+        $this->getClient()->withClientId('5');
+        $this->getClient()->withClientSecret('jejmtAJJWeEesW1siWwojjLn6zW9AIcWH1wqfFPq');
+        $this->registerResult($result = $this->getClient()->retrievingToken('client_credentials', [
+            'scope' => '',
+        ]));
+        $this->assertTrue($result->success());
+        $this->assertNotEmpty($result->data()->access_token);
+    }
+}