added DiffTaskResult Entity and Mapper

lib/Db/DiffTaskResultMapper.php

@@ -0,0 +1,36 @@
+<?php
+namespace OCA\GroupfolderFilesystemSnapshots\Db;
+
+use OCP\IDBConnection;
+use OCP\AppFramework\Db\QBMapper;
+
+/**
+ * @extends QBMapper<DiffTaskResult>
+ */
+class DiffTaskResultMapper extends QBMapper {
+
+    public function __construct(IDBConnection $db) {
+        parent::__construct($db, 'groupfolder_snapshots_task_results', DiffTaskResult::class);
+    }
+
+    public function find(int $id) {
+        $qb = $this->db->getQueryBuilder();
+
+        $qb->select('*')
+             ->from($this->getTableName())
+             ->where($qb->expr()->eq('id', $qb->createNamedParameter($id)));
+
+        return $this->findEntity($qb);
+    }
+
+    public function findAll(int $taskId) {
+        $qb = $this->db->getQueryBuilder();
+
+        $qb->select('*')
+           ->from($this->getTableName())
+           ->where($qb->expr()->eq('task_id', $qb->createNamedParameter($taskId)));
+
+        return $this->findEntities($qb);
+    }
+
+}