proxy support

[rcchopra]

No description provided.

[Copilot]

Pull Request Overview

This PR adds proxy support to the GitHub SCM driver by implementing a new proxy transport mechanism. The implementation allows HTTP requests to be routed through a specified proxy server while maintaining backward compatibility with existing code.

Key changes:

• New proxy transport package with configurable proxy URL support
• Extended GitHub driver API with proxy-enabled constructors
• Comprehensive test coverage for proxy functionality

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
scm/transport/proxy/proxy.go	Implements the core proxy transport functionality with Transport struct and NewTransport factory function
scm/transport/proxy/proxy_test.go	Provides comprehensive test coverage for proxy transport including edge cases and validation
scm/driver/github/github.go	Extends GitHub driver with NewWithProxy and NewDefaultWithProxy functions for proxy support

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