Using Workspace Connections for Docker Authentication in Serverless Builds

## Title
How to properly pass workspace connection credentials to Docker builds on AML serverless compute

## Description

### Problem Statement
I'm trying to set up a Docker build on Azure ML serverless compute that needs to authenticate to a private PyPI feed during the image build phase. The image needs to install Python packages from a private Azure DevOps Artifacts feed.

### What I'm Trying to Achieve
- Create a Docker image that installs packages from a private PyPI mirror
- Use Azure DevOps Personal Access Token (PAT) for authentication (I am happy to use a different way if it is more sustainable and better)
- Run this on AML serverless compute (not a dedicated compute cluster)
- Securely pass credentials without hardcoding them