header;
this was wrongly closing connections for HTTP/1.1 connections which
didn't send a "Connection" header; according to spec, the default is
"Keep-Alive", contrary to HTTP/1.0
This logic was extracted from the vanilla httpx build to a plugin to
make the gem "leaner", by removing "http_form_data" as a hard
dependency.
The multipart plugin still requires one to install it though, but if you
don't need to upload files, you don't have to install the gem anymore