Allow Logging to stdout with separate Error Log Channel (#718)

* Add dedicated error logging writer

* Document new errors to stdout flag

* Update changelog

* Thread-safe the log buffer

* Address feedback

* Remove duplication by adding log level

* Clean up error formatting

* Apply suggestions from code review

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

pkg/validation/logging.go

@@ -40,11 +40,12 @@ func configureLogger(o options.Logging, msgs []string) []string {
 
 	// Supply a sanity warning to the logger if all logging is disabled
 	if !o.StandardEnabled && !o.AuthEnabled && !o.RequestEnabled {
-		logger.Print("Warning: Logging disabled. No further logs will be shown.")
+		logger.Error("Warning: Logging disabled. No further logs will be shown.")
 	}
 
 	// Pass configuration values to the standard logger
 	logger.SetStandardEnabled(o.StandardEnabled)
+	logger.SetErrToInfo(o.ErrToInfo)
 	logger.SetAuthEnabled(o.AuthEnabled)
 	logger.SetReqEnabled(o.RequestEnabled)
 	logger.SetStandardTemplate(o.StandardFormat)

pkg/validation/options.go

@@ -92,7 +92,7 @@ func Validate(o *options.Options) error {
 				Do().
 				UnmarshalJSON()
 			if err != nil {
-				logger.Printf("error: failed to discover OIDC configuration: %v", err)
+				logger.Errorf("error: failed to discover OIDC configuration: %v", err)
 			} else {
 				// Prefer manually configured URLs. It's a bit unclear
 				// why you'd be doing discovery and also providing the URLs