Backfilled the members last_seen_at column

refs https://github.com/TryGhost/Team/issues/1305

- Skipped sqlite3 compatibility due to the lack of join support in update
- Uses a raw migration to improve performance

core/server/data/migrations/versions/4.37/2022-02-21-09-53-backfill-members-last-seen-at-column.js

@@ -0,0 +1,31 @@
+const logging = require('@tryghost/logging');
+const {createTransactionalMigration} = require('../../utils');
+
+module.exports = createTransactionalMigration(
+    async function up(knex) {
+        if (knex.client.config.client === 'sqlite3') {
+            logging.warn('Skipping migration for SQLite3');
+            return;
+        }
+        logging.info('Backfilling the members.last_seen_at column from members_login_events.');
+        await knex.raw(`
+            UPDATE members
+                INNER JOIN (SELECT member_id as id, MAX(created_at) as last_seen_at
+                    FROM members_login_events
+                    GROUP BY member_id) as logins ON logins.id = members.id
+            SET
+                members.last_seen_at = logins.last_seen_at
+            WHERE
+                members.last_seen_at IS NULL
+                    OR members.last_seen_at < logins.last_seen_at
+        `);
+    },
+    async function down(knex) {
+        if (knex.client.config.client === 'sqlite3') {
+            logging.warn('Skipping migration for SQLite3');
+            return;
+        }
+        logging.info('Rolling back the backfilling of the members.last_seen_at column from members_login_events.');
+        await knex('members').update({last_seen_at: null});
+    }
+);