**Use case**
ClickHouse as a web server becomes a viable scenario.
(At least in backoffice).

**Describe the solution you'd like**
Add this field.

**Additional context**
It's in question how to name it. The original HTTP specs has the famous typo in it and name it `referer`. While JavaScript has this typo fixed and name it `referrer`.

{"http_user_agent", std::make_shared<DataTypeString>()},
        {"forwarded_for", std::make_shared<DataTypeString>()},
        {"quota_key", std::make_shared<DataTypeString>()},
        {"elapsed", std::make_shared<DataTypeFloat64>()},
        {"is_cancelled", std::make_shared<DataTypeUInt8>()},
        {"read_rows", std::make_shared<DataTypeUInt64>()},
        {"read_bytes", std::make_shared<DataTypeUInt64>()},
        {"total_rows_approx", std::make_shared<DataTypeUInt64>()},
        {"written_rows", std::make_shared<DataTypeUInt64>()},
        {"written_bytes", std::make_shared<DataTypeUInt64>()},
        {"memory_usage", std::make_shared<DataTypeInt64>()},
        {"peak_memory_usage", std::make_shared<DataTypeInt64>()},
        {"query", std::make_shared<DataTypeString>()},
        {"thread_ids", std::make_shared<DataTypeArray>(std::make_shared<DataTypeUInt64>())},
        {"ProfileEvents.Names", std::make_shared<DataTypeArray>(std::make_shared<DataTypeString>())},
        {"ProfileEvents.Values", std::make_shared<DataTypeArray>(std::make_shared<DataTypeUInt64>())},
        {"Settings.Names", std::make_shared<DataTypeArray>(std::make_shared<DataTypeString>())},
        {"Settings.Values", std::make_shared<DataTypeArray>(std::make_shared<DataTypeString>())},
    };
}
void StorageSystemProcesses::fillData(MutableColumns & res_columns, const Context & context, const SelectQueryInfo &) const
{
    ProcessList::Info info = context.getProcessList().getInfo(true, true, true);
    for (const auto & process : info)
    {
        size_t i = 0;
        res_columns[i++]->insert(process.client_info.query_kind == ClientInfo::QueryKind::INITIAL_QUERY);
        res_columns[i++]->insert(process.client_info.current_user);
        res_columns[i++]->insert(process.client_info.current_query_id);
        res_columns[i++]->insertData(IPv6ToBinary(process.client_info.current_address.host()).data(), 16);