The header size and the idle time as settings (closes #70)

SWWAF_CLIENT_REQUEST_HEADER_MAX_BYTES (default 32K) and
SWWAF_CLIENT_IDLE_TIMEOUT (default 120s) replace the two values the
proxy fixed, and are read like the other size and duration settings.

Go's server reads 4K past the header limit it is given before it
refuses, so it is still given the setting less 4K, and a header size
of 4K or less, or off, stops the start. The idle time can be off.

README.md lists both settings and no longer calls them fixed.

Model: opus-5-5

internal/proxy/timeouts_test.go

@@ -273,3 +273,26 @@ func TestClientTooSlowToTakeTheAnswer(t *testing.T) {
 	wantTimedOut(t, start)
 	wantLine(t, line, http.StatusOK, requestlog.ActionTimedOut)
 }
+
+func TestClosesAnIdleConnection(t *testing.T) {
+	t.Parallel()
+
+	app := startApp(t, func(http.ResponseWriter, *http.Request) {})
+	addr, _ := startProxy(t, app.URL, map[string]string{
+		clientIdleTimeout: shortTimeoutSetting,
+	})
+
+	// The idle time starts once the answer is sent, so after start.
+	start := time.Now()
+	conn := dial(t, addr)
+	send(t, conn, "GET / HTTP/1.1\r\nHost: app\r\n\r\n")
+	wantStatus(t, readResponse(t, conn), http.StatusOK)
+
+	// The read deadline readResponse set still bounds this read.
+	_, err := conn.Read(make([]byte, 1))
+	if !errors.Is(err, io.EOF) {
+		t.Fatalf("read on the idle connection: %v, want it closed", err)
+	}
+
+	wantTimedOut(t, start)
+}