Function vformat_message

test/format-test.cc:2003–2008

auto format_as(test_enum e) -> int { return e; }

std::string vformat_message(int id, const char* format, fmt::format_args args) {
  auto buffer = fmt::memory_buffer();
  fmt::format_to(fmt::appender(buffer), "[{}] ", id);
  vformat_to(fmt::appender(buffer), format, args);
  return to_string(buffer);
}

template <typename... Args>
std::string format_message(int id, const char* format, const Args&... args) {