Upgrade to some new nextcloud standards

lib/Db/Color.php

@@ -0,0 +1,19 @@
+<?php
+namespace OCA\QuickNotes\Db;
+
+use JsonSerializable;
+
+use OCP\AppFramework\Db\Entity;
+
+class Color extends Entity implements JsonSerializable {
+
+	protected $color;
+
+	public function jsonSerialize() {
+		return [
+			'id' => $this->id,
+			'color' => $this->color
+		];
+	}
+
+}