Add support for private hex repos

[Munksgaard]

I've recently bought Oban Pro and integrated it in my application, only to realize that deps_nix seemingly doesn't support fetching hex packages from private repositories. Are there any plans to add such support?

For context, here is the setup steps that the Oban guide instructs you to do:

Authenticate to the private hex repo:

$ mix hex.repo add oban https://repo.oban.pro \
    --fetch-public-key SHA256:4/OSKi0NRF91QVVXlGAhb/BIMLnK8NHcx/EWs+aIWPc \
    --auth-key $OBAN_LICENSE_KEY

Add the oban_pro dependency to your mix.exs dependencies:

{:oban_pro, "~> 1.6", repo: "oban"}

[camelpunch]

I think the problem here is secrets management. It looks like you'd need that auth key inside the nix sandbox. You could achieve this with sops-nix or agenix.

I don't have a use for this feature myself, but would welcome a PR. I'm not sure what feature could be added that would be more elegant than overrideAttrs on a derivation, though.

[Munksgaard]

I don't have a use for this feature myself, but would welcome a PR. I'm not sure what feature could be added that would be more elegant than overrideAttrs on a derivation, though.

Ah, perhaps overrideAttrs could actually be enough to do what I want. If that's the case, a simple example in the README could go a long way. I'll see if I can cook something up at some point.