[#xxx] client: add error node maintenance

Signed-off-by: Viktor Nesterenko <vemeyzer@gmail.com>

client/errors.go

@@ -61,6 +61,13 @@ func IsErrSessionNotFound(err error) bool {
 	return wrapsErrType[*apistatus.SessionTokenNotFound](err)
 }
 
+// IsErrMaintenance checks if err corresponds to FrostFS status return
+// which tells that node is currently under maintenance. Supports wrapped
+// errors.
+func IsErrMaintenance(err error) bool {
+	return wrapsErrType[*apistatus.NodeUnderMaintenance](err)
+}
+
 // returns error describing missing field with the given name.
 func newErrMissingResponseField(name string) error {
 	return fmt.Errorf("missing %s field in the response", name)

client/errors_test.go

@@ -36,6 +36,9 @@ func TestErrors(t *testing.T) {
 		}, {
 			check: client.IsErrSessionNotFound,
 			err:   new(apistatus.SessionTokenNotFound),
+		}, {
+			check: client.IsErrMaintenance,
+			err:   new(apistatus.NodeUnderMaintenance),
 		},
 	}