Restore global logger state in tests

[jeffwidman]

Summary

Tests in several packages redirect the process-wide standard logger to capture output. Most did not restore the previous writer, so later tests could inherit a buffer owned by an earlier test. One OIDC registry test restored os.Stderr rather than the actual previous writer. TestSetupLogging also exercised production code that changes both standard-log and Logrus global configuration without restoring either logger.

This change adds shared test helpers that snapshot and restore:

• standard logger output, flags, and prefix
• Logrus output, formatter, level, and caller-reporting state

All direct output captures now use those helpers, and TestSetupLogging preserves state before invoking production setup. A focused helper test mutates every captured field in a subtest and verifies that cleanup restores the exact prior state.

The branch was rebased onto current main. During the audit of changes merged since the PR was opened, one additional NuGet test logger capture was found and migrated to the helper. No other uncovered global logger mutations remain in tests.

This does not make process-wide logger mutation safe for parallel tests. These tests should continue to run serially; the change prevents state from leaking after each test or subtest completes.

Validation

go test -race ./... -count=1

All packages pass.

[Copilot]

Pull request overview

Adds shared test helpers to prevent process-wide logger state from leaking between serial tests.

Changes:

• Snapshot and restore standard-log and Logrus configuration.
• Migrate all logger-capturing tests to shared helpers.
• Verify restoration of every captured logger field.

Show a summary per file

File	Description
proxy_test.go	Uses combined logger capture helper.
logging_test.go	Preserves logger state around logging tests.
internal/testhelpers/logging.go	Adds logger preservation and capture helpers.
internal/testhelpers/logging_test.go	Tests complete state restoration.
internal/oidc/oidc_registry_test.go	Restores the actual previous log writer.
internal/logging/logging_test.go	Uses standard-log capture helper.
internal/handlers/oidc_handling_test.go	Prevents OIDC test log leakage.
internal/handlers/nuget_feed_test.go	Prevents NuGet test log leakage.

Review details

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• Files reviewed: 8/8 changed files
• Comments generated: 0
• Review effort level: Balanced