WIP: Proxyauth fix

What does this MR do?

Allows GitLab users to declare usernames and passwords in the http_proxy and https_proxy connection string environment variables.

Without this merge request, users can set a connection string, but the username and password credentials are not passed through to the proxy request.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

GitLab advertises in its documentation that users can set proxy variables. However, when a user attempts to set a username/password, the credentials are not passed through to the library that handles the HTTP Proxy request. This fixes that error.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

#44573 (closed)