Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
{
    auto * logger = &Poco::Logger::get("SentryWriter");
    size_t size = 1024;
    char buffer[size];
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wformat-nonliteral"
#endif
    if (vsnprintf(buffer, size, message, args) >= 0)
    {
#ifdef __clang__
#pragma clang diagnostic pop
#endif
        switch (level)
        {
            case SENTRY_LEVEL_DEBUG:
                logger->debug(buffer);
                break;
            case SENTRY_LEVEL_INFO:
                logger->information(buffer);
                break;
            case SENTRY_LEVEL_WARNING:
                logger->warning(buffer);
                break;
            case SENTRY_LEVEL_ERROR:
                logger->error(buffer);