To handle 3 Million records in session table

### Describe the Improvement

We set 7d token expiry, and the session table generated 3 Million records in 3 days. It makes the database slow, timeout in the frontend application, and the site is unavailable during peak.

We suspect the slowness may be caused by the code trying to delete an expired token in the table during the auth login call, in line 220 in the authentication.ts.

await this.knex('directus_sessions').delete().where('expires', '<', new Date());

It could be better if we move above to a cronjob or create a database index for "expires" field.