chore(verifier): improve log (#497)

This PR improves log readability of the library.

Signed-off-by: Patrick Zheng <patrickzheng@microsoft.com>

verifier/verifier.go

@@ -407,7 +407,7 @@ func (v *verifier) processSignature(ctx context.Context, sigBlob []byte, envelop
 
 	var installedPlugin pluginframework.VerifyPlugin
 	if verificationPluginName != "" {
-		logger.Debugf("Finding verification plugin %s", verificationPluginName)
+		logger.Debugf("Finding verification plugin %q", verificationPluginName)
 		verificationPluginMinVersion, err := getVerificationPluginMinVersion(&outcome.EnvelopeContent.SignerInfo)
 		if err != nil && err != errExtendedAttributeNotExist {
 			return notation.ErrorVerificationInconclusive{Msg: fmt.Sprintf("error while getting plugin minimum version, error: %s", err)}
@@ -812,7 +812,7 @@ func revocationFinalResult(certResults []*revocationresult.CertRevocationResult,
 		certResult := certResults[i]
 		if certResult.RevocationMethod == revocationresult.RevocationMethodOCSPFallbackCRL {
 			// log the fallback warning
-			logger.Warnf("OCSP check failed with unknown error and fallback to CRL check for certificate #%d in chain with subject %v", (i + 1), cert.Subject)
+			logger.Warnf("OCSP check failed with unknown error and fallback to CRL check for certificate #%d in chain with subject %q", (i + 1), cert.Subject)
 		}
 		for _, serverResult := range certResult.ServerResults {
 			if serverResult.Error != nil {
@@ -821,10 +821,10 @@ func revocationFinalResult(certResults []*revocationresult.CertRevocationResult,
 					// when the final revocation method is OCSPFallbackCRL,
 					// the OCSP server results should not be logged as an error
 					// since the CRL revocation check can succeed.
-					logger.Debugf("Certificate #%d in chain with subject %v encountered an error for revocation method %s at URL %q: %v", (i + 1), cert.Subject, revocationresult.RevocationMethodOCSP, serverResult.Server, serverResult.Error)
+					logger.Debugf("Certificate #%d in chain with subject %q encountered an error for revocation method %s at URL %q: %v", (i + 1), cert.Subject, revocationresult.RevocationMethodOCSP, serverResult.Server, serverResult.Error)
 					continue
 				}
-				logger.Errorf("Certificate #%d in chain with subject %v encountered an error for revocation method %s at URL %q: %v", (i + 1), cert.Subject, serverResult.RevocationMethod, serverResult.Server, serverResult.Error)
+				logger.Errorf("Certificate #%d in chain with subject %q encountered an error for revocation method %s at URL %q: %v", (i + 1), cert.Subject, serverResult.RevocationMethod, serverResult.Server, serverResult.Error)
 			}
 		}
 
@@ -840,7 +840,7 @@ func revocationFinalResult(certResults []*revocationresult.CertRevocationResult,
 		}
 
 		if i < len(certResults)-1 && certResult.Result == revocationresult.ResultNonRevokable {
-			logger.Warnf("Certificate #%d in the chain with subject %v neither has an OCSP nor a CRL revocation method.", (i + 1), cert.Subject)
+			logger.Warnf("Certificate #%d in the chain with subject %q neither has an OCSP nor a CRL revocation method.", (i + 1), cert.Subject)
 		}
 	}
 	if revokedFound {