Support SMTP password via file path (Docker secrets support)

[tomgehrmann]

Currently, passwords need to be in plain text in the deployment env file.

Allowing the SMTP password to be alternatively provided via a file path (e.g. with env variable SMTP_PASSWORD_FILE) would enable secrets management support (with Docker secrets).

[micbar]

@flimmy @schweigisito Let us discuss that proposal.

[Lebowski89]

@micbar

Yes, please. _FILE for sensitive variables (or FILE__ in linuxserver style) so I can use docker secrets.

[cryinkfly]

I use this in my rootless podman quadlet file:

Environment=NOTIFICATIONS_SMTP_HOST=smtp.example.org
Environment=NOTIFICATIONS_SMTP_PORT=587
Environment=NOTIFICATIONS_SMTP_SENDER="OpenCloud Notifications <mail@example.com>"
Environment=NOTIFICATIONS_SMTP_USERNAME=mail@example.com
Secret=opencloud_smtp_pwd,type=env,target=NOTIFICATIONS_SMTP_PASSWORD
Environment=NOTIFICATIONS_SMTP_INSECURE=false
Environment=NOTIFICATIONS_SMTP_AUTHENTICATION=Login
Environment=NOTIFICATIONS_SMTP_ENCRYPTION=starttls

... and it works.