C++ API aborts due to incorrect noexcept specification

[arghness]

The C++ API can abort due to some throwing functions having a noexcept specification.

C++23 example, assuming a server is running on TCP port 9000:

#include <questdb/ingress/line_sender.hpp>

#include <print>
#include <utility>

int
main(int /*argc*/, char * /*argv*/[])
{
  try {
    auto sender = questdb::ingress::line_sender::from_conf("tcp::addr=localhost:9000;");
    sender.close();
    std::println("protocol_version={}", std::to_underlying(sender.protocol_version()));
  }
  catch (std::exception const &e) {
    std::println("Caught exception: {}", e.what());
  }

  return 0;
}

When run:

terminate called after throwing an instance of 'questdb::ingress::line_sender_error'
  what():  Sender closed.
Aborted (core dumped)

line_sender.protocol_version() and line_sender.new_buffer() are both declared as noexcept, but both call ensure_impl() which can throw. When it does, it causes the process to abort due to the incorrect exception specification.

I've made a PR with a fix at #130 which causes the exception to be caught without aborting.