📝 Add docstrings to 5.21-changes

Docstrings generation was requested by @karthikps97.

* #9293 (comment)

The following files were modified:

* `src/upgrade/upgrade_scripts/5.21.0/remove_datachunks_index.js`

Author: coderabbitai[bot]

src/upgrade/upgrade_scripts/5.21.0/remove_datachunks_index.js

@@ -0,0 +1,30 @@
+/* Copyright (C) 2025 NooBaa */
+"use strict";
+
+/**
+ * Drop the database index named "idx_btree_datachunks_dedup_key" if it exists.
+ *
+ * Executes the DROP INDEX operation against the connected database, logs success,
+ * and rethrows any error after logging it.
+ *
+ * @param {{dbg: object, db_client: object}} args - Utilities required to perform the upgrade: a logger (`dbg`) and a database client (`db_client`).
+ * @throws {Error} Re-throws any error encountered while executing the DROP INDEX statement.
+ */
+async function run({ dbg, db_client }) {
+  const indexName = 'idx_btree_datachunks_dedup_key';
+
+  try {
+    const pool = db_client.instance().get_pool();
+    await pool.query(`DROP INDEX IF EXISTS ${indexName};`);
+
+    dbg.log2("Executed upgrade script for dropping index ", indexName);
+  } catch (err) {
+    dbg.error('An error ocurred in the upgrade process:', err);
+    throw err;
+  }
+}
+
+module.exports = {
+  run,
+  description: 'Delete the "idx_btree_datachunks_dedup_key" index'
+};