fix: provide a writer for download fsim errors

[runcom]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @runcom, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the error handling mechanism for download operations, specifically addressing FDO (FIDO Device Onboard) simulation errors. By providing a custom io.Writer implementation, it ensures that any errors encountered during downloads are captured and logged using slog.Error, significantly improving the observability and debuggability of such failures.

Highlights

• Error Logging Improvement: Introduced a new errorLog type that implements the io.Writer interface, allowing for custom handling of download-related errors.
• Structured Error Reporting: Integrated the errorLog into the fdo.DownloadConfig within the transferOwnership2 function, ensuring that download errors are now directed to slog.Error for structured logging.
• Dependency Update: Added an import for the bytes package to support the new error logging functionality.

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[gemini-code-assist]

Code Review

This pull request introduces a custom io.Writer to pipe errors from the fsim.Download module into slog. The implementation is straightforward and effectively solves the problem. I've made a couple of suggestions to improve the implementation: one to prevent logging empty messages, and another to use a more descriptive name for the new type to enhance code clarity.

[gemini-code-assist]

The name errorLog is a bit generic. Consider renaming it to slogErrorWriter to be more descriptive about its function: acting as an io.Writer that forwards messages to slog.Error. This would improve code clarity and maintainability. You'll need to update the name here and on lines 37 and 299.

Suggested change

	type errorLog struct{}
	type slogErrorWriter struct{}