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. The idle time is read like the other durations, and can
be off.

Go's server reads 4K past the header limit it is given before it
refuses, so it is still given the setting less 4K. The header size
must be more than 4K and cannot be off; any other value stops the
start with a message that does not offer off.

SPEC.md and README.md say so. README.md lists both settings, no longer
calls them fixed, and names them as built.

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)
+}