Keep the bans, the clients and GeoJS's answers in state files (closes #17)

smallwebwaf now copies its state to bans.json, clients.json and
lookups.json in SWWAF_STATE_DIR, as "Persistent state" in SPEC.md
describes, and reads them back at start, so a restart lifts no ban and
gives no client a fresh allowance. Each client gains a history, and a
ban's notes count the netblock's requests. bans.json is written
SWWAF_STATE_WRITE_DELAY after a ban, and every file every
SWWAF_STATE_COUNTER_INTERVAL and at the stop. A ban read back is masked
to its netblock and refuses every client in it. A file that does not
parse, an unknown version, an entry without a field it needs, or an
unwritable directory stops the start.

Deviation: no AS number or name, and no ban cause, reason or lifting yet.

Model: opus-5-5

internal/proxy/bans_test.go

@@ -133,7 +133,7 @@ func TestBanIsNotCountedAndResetsTheCounters(t *testing.T) {
 	s.get(client, http.StatusOK, requestlog.ActionForward)
 	s.get(client, http.StatusForbidden, requestlog.ActionRateLimited)
 
-	banned := proxy.LedgerOf(server).Bans(netip.MustParsePrefix(client + "/32"))
+	banned := server.Ledger.Bans(netip.MustParsePrefix(client + "/32"))
 	if len(banned) != 2 || banned[0].Notes.Refused != 3 {
 		t.Errorf("bans %+v, want two, the first with 3 requests refused", banned)
 	}
@@ -291,12 +291,15 @@ func TestBanNotes(t *testing.T) {
 				Status:    http.StatusForbidden,
 				UserAgent: userAgent,
 			},
+			// The one let through, the one that broke the limit and the two
+			// refused under the ban.
+			Requests:    4,
 			Refused:     2,
 			EarlierBans: 0,
 		},
 	}
 
-	ledger := proxy.LedgerOf(server)
+	ledger := server.Ledger
 
 	got := ledger.Bans(netblock)
 	if len(got) != 1 || got[0] != want {
@@ -361,7 +364,7 @@ func (c *clock) advance(d time.Duration) {
 // set to midnight, the start of a bucket in every window.
 func startWithClock(
 	t *testing.T, geojsURL string, env map[string]string,
-) (*sender, *clock, *http.Server) {
+) (*sender, *clock, *proxy.Server) {
 	t.Helper()
 
 	app := startApp(t, func(http.ResponseWriter, *http.Request) {})