Add migration to remove NID field from user

A requirement from client to remove the NID field since most of the contries are not really using it.

#6830

packages/migration/src/migrations/user-mgnt/20241007100507-remove-nid-field.ts

@@ -0,0 +1,42 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * OpenCRVS is also distributed under the terms of the Civil Registration
+ * & Healthcare Disclaimer located at http://opencrvs.org/license.
+ *
+ * Copyright (C) The OpenCRVS Authors located at https://github.com/opencrvs/opencrvs-core/blob/master/AUTHORS.
+ */
+
+import { Db, MongoClient } from 'mongodb'
+
+export const up = async (db: Db, client: MongoClient) => {
+  // Add migration logic for applying changes to the database
+  // This code will be executed when running the migration
+  // It can include creating collections, modifying documents, etc.
+  const session = client.startSession()
+  try {
+    await db.collection('users').updateMany(
+      { identifiers: { $exists: true } }, // Only affect documents that have the identifiers field
+      { $unset: { identifiers: '' } } // Remove the identifiers field
+    )
+  } finally {
+    await session.endSession()
+  }
+}
+
+export const down = async (db: Db, client: MongoClient) => {
+  // Add migration logic for reverting changes made by the up() function
+  // This code will be executed when rolling back the migration
+  // It should reverse the changes made in the up() function
+  const session = client.startSession()
+  try {
+    await db.collection('users').updateMany(
+      { identifiers: { $exists: false } }, // Only affect documents that no longer have the identifiers field
+      { $set: { identifiers: [] } } // Re-add identifiers as an empty array
+    )
+  } finally {
+    await session.endSession()
+  }
+}