Use environment variables for configuration

[akelge]

Specific Demand

If I wish to run it in Docker or Kubernetes, it would be nice to use env vars or a config file to configure the features

Implement Suggestion

Parse env vars with names like DUFS_FEATURE_WITH_DASH_REPLACED_WITH_UNDERSCORES like
DUFS_ALLOW_ALL=true or DUFS_AUTH_METHOD=digest
and possibly support also a config file, with the cli flags in lowercase and with dash replaced by underscores, YAML or INI format.
In this case it would be nice to have a CLI flag like --config <configfile> and an env var like DUFS_CONFIGFILE=<configfile> and, maybe, a default path like ./config.yaml