void writeSite(string& site, const string& contentType);

no matching function for call to ‘writeSite(std::basic_ostringstream<char>::__string_type, const char [17])’
   writeSite(body.str(), "application/json");

std::ostringstream body;

  body << "{";

  // some more string building

  body << "}";

  std::string sbody = body.str();

  writeSite(sbody, "application/json");