Merge branch 'smu44-master-patch-44364' into 'master'

# To upgrade from ecloud 20.x.x.x to 21.0.9.12

- As usual, upgrade your OS with latest patchs, optionally take backup/snapshot

  - NB: you may want to filter out incomming email (TCP 25 & 587) during this upgrade, to avoid losing any messages in case of a rollback

- In your `docker-compose.yml` file update the following:

  - Set the redis image to `redis:6.2-alpine`

  - Set the welcome image to `registry.gitlab.e.foundation/e/infra/docker-welcome:2.5.0`

- Run `docker-compose pull`

- Run `docker-compose up -d`

- Examine `docker-compose logs --tail=500 nextcloud` for the following messages:

  - `nextcloud       | Upgrading nextcloud from x.x.x.x ...` (x.x.x.x is your previous Nextcloud version)

  - `nextcloud       | Update successful`

- Enable the `ecloud-accounts` app:

  `docker exec -u www-data nextcloud /var/www/html/occ app:enable ecloud-accounts`

- Run `docker exec -T --user www-data nextcloud php occ db:add-missing-indices`