httpd_ws_frame struct

Final frame: For received frames this field indicates whether the `FIN` flag was set. For frames to be transmitted, this field is only used if the `fragmented` option is set as well. If `fragmented` is false, the `FIN` flag is set by default, marking the ws_frame as a complete/unfragmented message (esp_http_server doesn't automatically fragment messages).

Indication that the frame allocated for transmission is a message fragment, so the `FIN` flag is set manually according to the `final` option. This flag is never set for received messages.

WebSocket frame type.

Pre-allocated data buffer.

Length of the WebSocket data.