Add advss namespace

Fixes name conflict with "Duration" class and typedef of the same name
on MacOS

src/utils/math-helpers.hpp

@@ -3,7 +3,11 @@
 #include <variant>
 #include <optional>
 
+namespace advss {
+
 std::variant<double, std::string>
 EvalMathExpression(const std::string &expression);
 bool IsValidNumber(const std::string &);
 std::optional<double> GetDouble(const std::string &);
+
+} // namespace advss