Pass OIDC environment variables to proxy

[JamieMagee]

This change passes the ACTIONS_ID_TOKEN_REQUEST_TOKEN and ACTIONS_ID_TOKEN_REQUEST_URL from GitHub Actions to the Dependabot proxy container.

It's the first part of the feature to allow to proxy to use OIDC federated credentials for authentication to private registries.

References:

• Configuring OpenID Connect in cloud providers
• OpenID Connect reference

[Copilot]

Pull Request Overview

This PR adds support for GitHub Actions OpenID Connect (OIDC) token functionality by passing OIDC environment variables to the Dependabot proxy container. This enables secure authentication with cloud providers using OIDC tokens instead of long-lived credentials.

Key changes:

• Pass ACTIONS_ID_TOKEN_REQUEST_TOKEN and ACTIONS_ID_TOKEN_REQUEST_URL environment variables to the proxy container
• Add comprehensive test coverage for OIDC environment variable forwarding

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/proxy.ts	Adds OIDC environment variables to proxy container configuration and reorganizes imports
tests/proxy-integration.test.ts	Adds integration tests for OIDC environment variable forwarding and reorganizes imports

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