Upgrade to some new nextcloud standards

lib/Db/NoteTag.php

@@ -0,0 +1,23 @@
+<?php
+namespace OCA\QuickNotes\Db;
+
+use JsonSerializable;
+
+use OCP\AppFramework\Db\Entity;
+
+class NoteTag extends Entity implements JsonSerializable {
+
+	protected $noteId;
+	protected $tagId;
+	protected $userId;
+
+	public function jsonSerialize() {
+		return [
+			'id' => $this->id,
+			'noteid' => $this->noteId,
+			'tagid' => $this->tagId,
+			'userid' => $this->userId
+		];
+	}
+
+}