HTTPS Client is not compliant with HTTP 1.1

[gregjesl]

We've been using your example with great success for a while but have recently run into an issue with file downloads. After digging in to the issue, it turns out the https_client used in this example is not compliant with HTTP 1.1.

Per the HTTP 1.1 spec:

All HTTP/1.1 applications MUST be able to receive and decode the "chunked" transfer-coding, and MUST ignore chunk-extension extensions they do not understand.

When a response is chunked, no Content-Length header is sent (see here for more details); however, the HTTPS client will fail if the Content-Length header is not set in the response:

esp32-ota-https/main/https_client.c

Lines 215 to 225 in 88c001b

	// We're mainly interested in the content length.
	// The server should either send the Content-Length header or should close the connection at the end.
	int contentLength = 0;
	if (!http_parse_key_value_int(httpRequest->response_buffer, "Content-Length:", &contentLength)) {
	ESP_LOGD(TAG, "Content-Length: %d", contentLength);
	httpContext->content_length = contentLength;
	} else {
	ESP_LOGW(TAG, "Content length header missing, dropping the packet. '%s'", httpRequest->response_buffer);
	// TODO error callback??
	return 0;
	}