EVEREST-664 Improve error message (#380)

api/database_cluster_restore.go

@@ -71,7 +71,7 @@ func (e *EverestServer) CreateDatabaseClusterRestore(ctx echo.Context) error {
 	if dbCluster.Status.Status == everestv1alpha1.AppStateRestoring {
 		e.l.Error("failed creating restore because another one is in progress")
 		return ctx.JSON(http.StatusBadRequest, Error{
-			Message: pointer.ToString("Another restore is in progress"),
+			Message: pointer.ToString("Another restore process for this DB cluster is currently in progress. Wait for its completion before initiating another."),
 		})
 	}