enhancement: Add conditional test logging via environment variable

[jamestexas]

Problem

The test suite contains many t.Logf() statements that are helpful for debugging but can be noisy during normal test runs. Currently, there's no way to conditionally enable/disable verbose test output.

Proposed Solution

Add support for conditional test logging via environment variable:

// Helper function
func logIfVerbose(t *testing.T, format string, args ...interface{}) {
    t.Helper()
    if os.Getenv("CMS_TEST_VERBOSE") == "1" {
        t.Logf(format, args...)
    }
}

// Usage in tests
logIfVerbose(t, "✓ SignDataWithSigner produced valid CMS signature")
logIfVerbose(t, "CMS signature length: %d bytes", len(signature))

Benefits

• Cleaner test output by default (no debug logs)
• Easy debugging when needed: CMS_TEST_VERBOSE=1 go test
• Maintains existing debugging information for troubleshooting test failures
• Consistent with Go testing patterns (similar to -v flag but more granular)

Implementation Notes

• Add logIfVerbose helper to signer_test.go and verifier_test.go
• Replace existing t.Logf() calls with logIfVerbose()
• Document in test files and potentially in README/CONTRIBUTING.md
• Could also support levels: CMS_TEST_VERBOSE=2 for even more detailed output

Related

This came up during code review feedback on PR #6 where Copilot suggested removing test logging statements. This enhancement would satisfy both needs: keep the valuable debugging info but make it opt-in.