Structured logging adapter for C++

LogContext.h

#pragma once

#include <vector>
#include <string>
#include <iostream>

class LogContext
{
  public:
template <typename T>
LogContext With(const std::string&, T) const;
friend std::ostream& operator<<(std::ostream&, const LogContext&);
  private:
std::vector<std::pair<<std::string, std::string>> metadata;
};

template <typename T>
inline LogContext LogContext::With(const std::string& key, T value) const
{
    auto ctx = *this;
    std::stringstream ss;
    ss << std::boolalpha << value;
    ctx.metadata.push_back({key, ss.str()});
    return ctx;
}

template <>
inline LogContext LogContext::With(const std::string& key, uint8_t value) const
{
    auto ctx = *this;
    ctx.metadata.push_back({key, std::to_string(value)});
    return ctx;
}

inline std::ostream& operator<<(std::ostream& os, const LogContext& ctx)
{
    for(const auto& kvPair : ctx.metadata) {
        os << kvPair.first << "=";
        bool valueContainsSpaces = kvPair.second.find(' ') != std::string::npos;
        if (valueContainsSpaces) {
            os << '"';
        }
        os << kvPair.second;
        if (valueContainsSpaces) {
            os << '"';
        }
        os << ' ';
    }
    return os;
}

main.cpp

#include <iostream>
#include "LogContext.h"

int main(int argc, char** argv) {
  auto ctx = LogContext().With("connectionId", "abcdef").With("sessionId", 1235123).With("outbound", true);
  std::cout << ctx.With("msg", "this is a test message") << std::endl;
}