Allow specifying "secret" config variable as an environment variable

[ustun]

Edit: Realized this is already supported. Sorry for the noise.

Expected Behavior

The config var secret is used for proxy and cookie authentication. It would be great if this could be provided just like ADMIN_PASSWORD.

For example, in a cloud environment using K8S, this env var would be supplied via the Secret Manager.

Current Behavior

One can only specify ADMIN_USERNAME and PASSWORD, but not the secret.

Possible Solution

Specifying SECRET adds/replaces the secret in ini files.