Authentication token sources

[s-hamann]

The CLI accepts the authentication token as a command line parameter (which exposes the secret to the process list) or from a file (which requires it to be written to a plain text file). At least on Linux systems, the latter is surprisingly flexible, since it also allows passing a file descriptor that is filled by some other process. It's not very intuitive, though.
I'd be nice to directly support getting the secret from an environment variable (for easier use in containers) or a command (so people can hook up their password manager/secret vault/...).