Add getting user/pass info from environent variables.

[pataquets]

Useful both for Docker usage and for existing enviornment variable secrets workflows.

Works the same as EDITOR, overriding anything if present.

[samuelallan72]

@pataquets I'm not sure this is a great idea, because otherwise gradually users will want more and more configuration options exposed as environment variables. Maybe we can find a more general method here that's more compatible with existing use?

Note also that there is the cfg_sn_password_eval config option which runs a command to get the password, so the password doesn't need to be stored in the config file.

[cfoust]

Personally providing a way to eval the username too would be useful. I'm not sure how I feel about needing to have my username in my dotfiles.

[pataquets]

I see your point, @swalladge. However, I think that enabling the env var option just for these it's an acceptable exception, since both options are sensitive values, although some might consider usernames not to be, I lean more in considering username also sensitive info. If you find this applies to cfg_sn_password_eval option, I'll be glad to add it, btw.

Anyway, there are not that many options that would prevent anyone else adding their own, if needed. I must admit I don't fully understand your concern here, since I fail to see how a 'more general method' would be, due to my limited Python experience.

Also, this PR is more targeted to enable a self-contained, Docker image build and run method (to follow up next as a PR), which would enable another running method, with 'just Docker required' (no Python/Pip/whatever required). I was aware of cfg_sn_password_eval, but it made this use-case more complex, thou.

[samuelallan72]

@pataquets thanks for your contribution!

[pataquets]

Don't mention it, @swalladge. Happy to be able to give back and thank you for sharing such an useful software.