return values for all functions in the codebase (#234)

Author: shaleenji

src/utils/types.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <variant>
+
+namespace ndd {
+
+template <typename T = std::monostate>
+struct OperationResult {
+    unsigned int code = 0;
+    std::string message;
+    std::optional<T> value;
+
+    bool ok() const { return code == 0; }
+};
+
+}  // namespace ndd