Ability to override http_proxy/https_proxy to reach Vault

[davidducros]

Is your feature request related to a problem? Please describe.

I work in an enterprise where different multiple http proxies are involved in connecting to different services. Specifically one proxy for accessing the internet (for access to AWS/GCP/Azure etc) and one for accessing security resources like our instance of HashiCorp Vault.

Describe the solution you'd like

I would like the ability to override the http proxy used by the Vault APIs, specifically when used via the terraform provider although this all ends up in the same api/client.go code anyway.

Additional context

This was originally requested via an issue on the terraform provider repo here: hashicorp/terraform-provider-vault#1150
An implementation using a new VAULT_HTTP_PROXY has been provided here: #12582