feat(config): Make config elements overridable via environment variable

[kreusel]

As for many (or just my) environments, you do not want to have passwords in configurations that may be stored in a git repository. So i wanted to have a way of configuring env var replacements inside the .toml file without changing to much.

Another possible solution would be to implement a more sophisticated config framework.

Example for config file (smtp_password will get replaced with value of $SMTP_PASSWORD):

[nodemailer]
smtp_server = "mail.example.com"
smtp_port = "587"
smtp_username = "noreply@example.com"
smtp_password = "$SMTP_PASSWORD"

[lowercasename]

Ah, this is a lovely idea. I wonder if it would be a bit safer to parse the file as TOML first, and then replace the variables in the output JS object, knowing that they specifically start with a $ symbol. My worry here is what happens if I put a $ symbol in another variable, or in an API key, etc.

[kreusel]

Fair point, had that idea too. Will have a look