added docs and tests for mqtt library, small fixes (removed warnings, option for custom outbox, websocket bug fixed for longer transports). refactored to use common tcp_transport component, support for CMake build system.
Closes#2108
`esp_http_client_write` API puts a constraint on the maximum length of the data that can be
written, which is equal to client handle buffer size, but the data to be sent can be more
than that, so in this case, this API has to be called multiple times.
In `esp_http_client_open` API, the return value of `transport_write` API, used to send HTTP
request, is not checked, and in rare cases, data written will be less than expected which will
cause a problem. So there are fixes for these minor issues in this MR.
- A bug of the http client when it downloads a chunked encoding packet is greater than the http_client's buffer, http_parser will call the callback body more than once, and the client will only handle the last
- with ssl_read, need to check before read to avoid timeout blocked when no data for reading
Add error handling for http client
set ssid password correct with Example_WIFI test, and clear password before free
Fixed the CI failure due to HTTP errror names
