Register nextcloud capabilities to check api versions..

<?xml version="1.0"?>
<ocs>
  ...
  <capabilities>
   ...
   <quicknotes>
    <version>0.6.0</version>
    <api_version>1.0</api_version>
   </quicknotes>
   ...
  </capabilities>
</ocs>

lib/AppInfo/Capabilities.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types=1);
+/*
+ * @copyright 2016-2020 Matias De lellis <mati86dl@gmail.com>
+ *
+ * @author 2016 Matias De lellis <mati86dl@gmail.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+namespace OCA\QuickNotes\AppInfo;
+
+use OCP\Capabilities\ICapability;
+use OCP\App\IAppManager;
+
+class Capabilities implements ICapability {
+
+	/** @var IAppManager */
+	private $appManager;
+
+	public function __construct(IAppManager $appManager) {
+		$this->appManager = $appManager;
+	}
+
+	public function getCapabilities() {
+		return [
+			Application::APP_ID => [
+				'version' => $this->appManager->getAppVersion(Application::APP_ID),
+				'api_version' => Application::API_VERSION,
+			],
+		];
+	}
+
+}