added migration

migrations/20241216212401-remove-documents-with-non-existent-users.js

@@ -0,0 +1,21 @@
+module.exports = {
+  async up(db) {
+    const allUsers = await db
+      .collection('users')
+      .find({}, { projection: { _id: 1 } })
+      .toArray()
+    const allUserIds = allUsers.map((user) => user._id.toString())
+    const collections = ['attachments', 'courses', 'lessons', 'notes', 'questions', 'quizzes', 'resourcescategories']
+    for (const collectionName of collections) {
+      const authorsFromCollection = await db.collection(collectionName).distinct('author')
+      const nonExistingUsers = await authorsFromCollection.filter((userId) => !allUserIds.includes(userId.toString()))
+
+      if (nonExistingUsers.length > 0) {
+        await db.collection(collectionName).deleteMany({ author: { $in: nonExistingUsers } })
+      }
+      console.log(`Removed ${nonExistingUsers.length} non-existing users from collection ${collectionName}`)
+    }
+  },
+
+  async down() {}
+}