Add opt save global log output to file (#2115)

close  #1933

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*Sponsored by Kithara Software GmbH*

agent/rpc/auth_interceptor.go

@@ -2,9 +2,9 @@ package rpc
 
 import (
 	"context"
-	"log"
 	"time"
 
+	"github.com/rs/zerolog/log"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/metadata"
 )
@@ -93,7 +93,7 @@ func (interceptor *AuthInterceptor) refreshToken() error {
 	}
 
 	interceptor.accessToken = accessToken
-	log.Printf("Token refreshed: %v", accessToken)
+	log.Debug().Msgf("Token refreshed: %v", accessToken)
 
 	return nil
 }