Add a new endpoint to retrieve information from the wallabag instance

Useful for api client which required some information.
We might add more inside them in the future.

The endpoint /api/version should be avoided now as it contains not so much information rather the version.

tests/Wallabag/ApiBundle/Controller/WallabagRestControllerTest.php

@@ -18,4 +18,21 @@ class WallabagRestControllerTest extends WallabagApiTestCase
 
         $this->assertSame($client->getContainer()->getParameter('wallabag_core.version'), $content);
     }
+
+    public function testGetInfo()
+    {
+        // create a new client instead of using $this->client to be sure client isn't authenticated
+        $client = static::createClient();
+        $client->request('GET', '/api/info');
+
+        $this->assertSame(200, $client->getResponse()->getStatusCode());
+
+        $content = json_decode($client->getResponse()->getContent(), true);
+
+        $this->assertArrayHasKey('appname', $content);
+        $this->assertArrayHasKey('version', $content);
+        $this->assertArrayHasKey('allowed_registration', $content);
+
+        $this->assertSame('wallabag', $content['appname']);
+    }
 }