[FEATURE] Support *_PROXY env variables

[DenisBY]

Is your feature request related to a problem?

I tried to debug the provider using mitm proxy with HTTPS_PROXY=http://localhost:8080 terraform apply and was very confused when I didn't find any connections to OS from the provider until I specified proxy= option in config

What solution would you like?

The provider should support proxy config from *_PROXY env variables beside proxy= option

[prudhvigodithi]

[Untriage]
Hey @DenisBY can you please share the full config (the .tf file you are using?) is the OS cluster behind a reverse proxy or you are trying to access the cluster thought a proxy ?
Adding @timwisbauer-contsec as we contributed the proxy support feature.
Thank you

[DenisBY]

Hi. I was trying to debug one thing and used MITM proxy via HTTPS_PROXY=http://localhost:8080 terraform apply command and was wonder, why I can see connections only from terraform itself and from aws provider and nothing from opensearch provider. And only after some digging, I found that I need to explicitly set proxy= in config for OS provider. It would be nice if OS provider also check for *_PROXY variables and get proxy settings from there if found.

[prudhvigodithi]

Hey @DenisBY the proxy feature was actually contributed in this PR #95, can you please check if you can enhance to use HTTPS_PROXY variable.
Adding @timwisbauer-contsec.
Thank you

[gnuletik]

Should be fixed with #217

You can test it with my fork: https://registry.terraform.io/providers/gnuletik/opensearch/latest/docs
Latest version ship these two PR:

• fix: support proxy env vars #217
• fix: no credentials provider in chain when not using a profile #218