[#36] Move log messages to constants

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

metrics/service.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"net/http"
 
+	"git.frostfs.info/TrueCloudLab/frostfs-http-gw/internal/logs"
 	"go.uber.org/zap"
 )
 
@@ -24,21 +25,21 @@ type Config struct {
 // Start runs http service with the exposed endpoint on the configured port.
 func (ms *Service) Start() {
 	if ms.enabled {
-		ms.log.Info("service is running", zap.String("endpoint", ms.Addr))
+		ms.log.Info(logs.ServiceIsRunning, zap.String("endpoint", ms.Addr))
 		err := ms.ListenAndServe()
 		if err != nil && err != http.ErrServerClosed {
-			ms.log.Warn("service couldn't start on configured port")
+			ms.log.Warn(logs.ServiceCouldntStartOnConfiguredPort)
 		}
 	} else {
-		ms.log.Info("service hasn't started since it's disabled")
+		ms.log.Info(logs.ServiceHasntStartedSinceItsDisabled)
 	}
 }
 
 // ShutDown stops the service.
 func (ms *Service) ShutDown(ctx context.Context) {
-	ms.log.Info("shutting down service", zap.String("endpoint", ms.Addr))
+	ms.log.Info(logs.ShuttingDownService, zap.String("endpoint", ms.Addr))
 	err := ms.Shutdown(ctx)
 	if err != nil {
-		ms.log.Panic("can't shut down service")
+		ms.log.Panic(logs.CantShutDownService)
 	}
 }