message: Print timestamps with 0-padded milliseconds
diff: @@ -97,7 +97,10 @@ void stringification_inspector::consume(timestamp& x) {
  // time_t has no milliseconds, so we need to insert them manually.
  auto ms = (x.time_since_epoch().count() / 1000000) % 1000;
  result_ += '.';
  - result_ += std::to_string(ms);
  + auto frac = std::to_string(ms);
  + if (frac.size() < 3)
  + frac.insert(0, 3 - frac.size(), '0');
  + result_ += frac;
  }
  } // namespace detail
  