[#111] Use request scope logger

Store child zap logger with request scope fields into context.
Request scoped fields: request_id, api/method, bucket, object

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

api/handler/notifications.go

@@ -202,7 +202,7 @@ func (h *handler) checkBucketConfiguration(ctx context.Context, conf *data.Notif
 				return
 			}
 		} else {
-			h.log.Warn("failed to send test event because notifications is disabled")
+			h.reqLogger(ctx).Warn("failed to send test event because notifications is disabled")
 		}
 
 		if q.ID == "" {