Include plaintext_env_vars in nginx-cnb

[kvedurmu]

See this feature request in the CF NGINX Buildpack for context - cloudfoundry/nginx-buildpack#17. We should look into supporting this behavior in the NGINX Paketo Buildpack.

[kvedurmu]

@ForestEckhardt could you update this issue to make it a bit more clear? Thanks.

[ForestEckhardt]

@kvedurmu I have as much context as that issue unfortunately.

[fg-j]

This test added to the cloud foundry buildpack in the commit that resolves the CF buildpack issue sheds some light on the expected behaviour of this feature and some potential reproduction steps.

To reproduce, I think we need to build this cloud foundry buildpack test fixture with the CNB and evaluate whether the /test endpoint returns proper JSON or not.

[ForestEckhardt]

My understanding is that we are trying to move away from increased user interpolation in the nginx.conf and this seems antithetical to that idea. I would love to hear from my fellow @paketo-buildpacks/web-servers-maintainers and @ryanmoran about there feelings on this issue.