Add http proxy support as a config option

[dkronst]

Some setups require the use of fine grained proxy settings (and cannot rely on environment variables alone). This PR enables this as a config option.

Cheers!

Community Note

• Please vote on this pull request by adding a 👍 reaction to the original pull request comment to help the community and maintainers prioritize this request
• Please do not leave "+1" or other comments that do not add relevant new information or questions, they generate extra noise for pull request followers and do not help prioritize the request

Reference: #0000 <!--- Pull Requests should have an associated issue or may be closed --->

Please briefly describe the changes proposed in this pull request.

[hashicorp-cla]

All committers have signed the CLA.

[gdavison]

Looks good. Thanks for this, @dkronst! 🚀

[dkronst]

that's great! thanks @gdavison!