added Subscription Entity and Mapper

lib/Db/Subscription.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace OCA\DavPush\Db;
+
+use JsonSerializable;
+
+use OCP\AppFramework\Db\Entity;
+
+class Subscription extends Entity implements JsonSerializable {
+	protected $userId;
+	protected $collectionName;
+	protected $data;
+	protected $creationTimestamp;
+	protected $expirationTimestamp;
+
+	public function __construct() {
+		$this->addType('creationTimestamp','integer');
+		$this->addType('expirationTimestamp','integer');
+	}
+
+	public function jsonSerialize(): array {
+		return [
+			'id' => $this->id,
+			'userId' => $this->userId,
+			'collectionName' => $this->collectionName,
+			'data' => $this->data,
+			'creationTimestamp' => $this->creationTimestamp,
+			'expirationTimestamp' => $this->expirationTimestampv
+		];
+	}
+}

lib/Db/SubscriptionMapper.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace OCA\DavPush\Db;
+
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Db\Entity;
+use OCP\AppFramework\Db\QBMapper;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+
+class SubscriptionMapper extends QBMapper {	
+	public const TABLENAME = 'dav_push_subscriptions';
+
+	public function __construct(IDBConnection $db) {
+		parent::__construct($db, self::TABLENAME, Subscription::class);
+	}
+
+	/**
+	 * @param string $userId
+	 * @param string $id
+	 * @return Entity|Subscription
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 * @throws DoesNotExistException
+	 */
+	public function find(string $userId, int $id): Subscription {
+		/* @var $qb IQueryBuilder */
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')
+			->from(self::TABLENAME)
+			->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT)))
+			->andWhere($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)));
+		
+		return $this->findEntity($qb);
+	}
+}