`bitreq::Client` only reuses an HTTP/1.1 connection when the response explicitly contains `Connection: keep-alive`

[tnull]

corepc/bitreq/src/connection.rs

Lines 578 to 588 in 2d56a77

	let mut found_keep_alive = false;
	if let Some(header) = response.headers.get("connection") {
	if header.eq_ignore_ascii_case("keep-alive") {
	found_keep_alive = true;
	}
	}
	if !found_keep_alive {
	conn.permits.store(0, Ordering::Release);
	conn.readable_request_id.store(usize::MAX, Ordering::Release);
	} else {
	conn.readable_request_id.fetch_add(1, Ordering::Release);

HTTP/1.1 connections are persistent by default unless Connection: close is present. Servers such as Caddy therefore omit Connection: keep-alive. bitreq consequently marks a healthy socket unusable and performs a new TCP and TLS handshake for the next request.

Expected behavior:

• HTTP/1.1 or later: reuse unless Connection: close is present.
• HTTP/1.0: require explicit Connection: keep-alive.

RFC 9112 §9.3: https://www.rfc-editor.org/rfc/rfc9112.html#section-9.3

Related: #562

Will see to fix as part of #564.