External storage app saves password for all users in the database

How it was found

External storage (files_external) app save passwords of all users to database table "oc_credentials" even when "Log-in credentials, save in database" option is not used.

It's a security risk that allow password extraction of all users.

A local system admin that has access to database and nextcloud config file could decrypt any user password.

Steps to reproduce

1. Enable app "External storage support" (files_external).
2. Login to nextcloud.
3. User recoverable password will be saved to table "oc_credentials" at "password::logincredentials/credentials".

Expected behaviour

Don't save user password to table "oc_credentials" unless user has a mount with "Log-in credentials, save in database" option.

Actual behaviour

Passwords of all users is saved to table "oc_credentials" when files_external app is enabled.

Tested with

Nextcloud 18.0.4 + External storage 1.9.0 Nextcloud 17.0.5 + External storage 1.8.0

Impact

A local system admin could recover any user password.