[Amith211]

What are you trying to accomplish?

MyGet-hosted NuGet feeds redirect package downloads to their shared CDN at mgcdn-main2.azureedge.net.

Since Dependabot introduced outbound egress allowlist enforcement, these redirects are blocked with 403 Forbidden, preventing dependency updates and, in some cases, the initial NuGet package restore.

This issue has been reproduced across multiple repositories using the Caliburn.Micro MyGet feed.

This PR adds mgcdn-main2.azureedge.net as a derived URL for .myget.org registries, allowing Dependabot to download packages from MyGet's CDN.

Anything you want to highlight for special attention from reviewers?

The URL is added under registry_redirect_derivations rather than the global nuget allowlist.

This restricts access to the CDN to Dependabot jobs configured with a matching MyGet registry, while supporting different MyGet feed subdomains.

How will you know you've accomplished your goal?

The following error should no longer occur when Dependabot downloads packages from MyGet:

302 https://www.myget.org/F/caliburn-micro-builds/...
GET https://mgcdn-main2.azureedge.net/...
* egress not allowlisted mgcdn-main2.azureedge.net
403 Forbidden

Testing

Successfully ran tests:

go test -race -shuffle=on -count=2 -v ./...

Result: PASS (exit code 0)

A test has been added to verify that the CDN hostname is correctly derived from a configured MyGet registry.

The test was verified using a red/green approach:

• Without the allowlist entry: The test fails as expected.
• With the allowlist entry: The test passes.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.