Some URLs expect a User-Agent header.

Example (version 22.2.1.3767):
```sql
SELECT * FROM url('https://api.github.com/users/clickhouse','JSONAsString');
```
Results in:
```
Code: 86. DB::Exception: Received error from remote server /users/clickhouse. HTTP status code: 403 Forbidden, body: 
Request forbidden by administrative rules. Please make sure your request has a User-Agent header (http://developer.github.com/v3/#user-agent-required). Check https://developer.github.com for other possible causes.
: While executing URL. (RECEIVED_ERROR_FROM_REMOTE_IO_SERVER) (version 22.2.1.3767)
```

Maybe it's nice to always send a header along, something like `User-Agent: ClickHouse/22.2.1.3767` ?

{
            
            NON_RETRIABLE_ERROR,
            
            SKIP_NOT_FOUND_URL,
            NONE,
        };
        InitializeError initialization_error = InitializeError::NONE;
    public:
        using NextCallback = std::function<void(size_t)>;
        using OutStreamCallback = std::function<void(std::ostream &)>;
        explicit ReadWriteBufferFromHTTPBase(
            UpdatableSessionPtr session_,
            Poco::URI uri_,
            const Poco::Net::HTTPBasicCredentials & credentials_,
            const std::string & method_ = {},
            OutStreamCallback out_stream_callback_ = {},
            size_t buffer_size_ = DBMS_DEFAULT_BUFFER_SIZE,
            const ReadSettings & settings_ = {},
            HTTPHeaderEntries http_header_entries_ = {},
            Range read_range_ = {},
            const RemoteHostFilter & remote_host_filter_ = {},
            bool delay_initialization = false,
            bool use_external_buffer_ = false,
            bool http_skip_not_found_url_ = false)