Function trim_copy

examples/server/httplib.h:2258–2261

}

inline std::string trim_copy(const std::string &s) {
  auto r = trim(s.data(), s.data() + s.size(), 0, s.size());
  return s.substr(r.first, r.second - r.first);
}

inline void split(const char *b, const char *e, char d,
                  std::function<void(const char *, const char *)> fn) {