Byte limits per client over a minute, an hour and a day (closes #20)

SWWAF_BYTES_LIMIT_PER_MINUTE, _PER_HOUR and _PER_DAY (10G, 20G, 50G)
and SWWAF_BYTES_COUNT (both). A request's bytes are counted once its
answer has ended, for a request passed to the app that the rate limits
count; what a WebSocket carries each way, once it closes. Bytes over a
limit ban the client as a broken rate limit does, and cut nothing
short. clients.json keeps the byte buckets, the log line's counts carry
the byte totals, ban notes say what the limit is on, and the limit hits
metric is labelled by kind.

Judgement call: limit_hit names a byte window minute_bytes, hour_bytes
or day_bytes, as counts names the byte totals.
Judgement call: in observe mode, the bytes of a request enforce mode
would have refused are not counted.

Model: opus-5-5

internal/metrics/metrics.go

@@ -6,6 +6,7 @@ package metrics
 import (
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -89,8 +90,9 @@ func New(topN int, instanceName string) *Metrics {
 			Help: "How long requests passed to the app took, from then to their end.",
 		}),
 		rateLimitHits: counterVec("smallwebwaf_rate_limit_hits_total",
-			"Requests that broke a rate limit, by its window.",
-			[]string{"window"}),
+			"Requests that broke a rate limit or a byte limit, by its window and "+
+				"its kind, requests or bytes.",
+			[]string{"window", "kind"}),
 		sizeAndTimeLimitHits: counterVec("smallwebwaf_size_and_time_limit_hits_total",
 			"Requests that passed a size or time limit, by its setting.",
 			[]string{"limit"}),
@@ -325,7 +327,15 @@ func (m *Metrics) RequestEnded(
 	}
 
 	if line.LimitHit != "" {
-		m.rateLimitHits.WithLabelValues(line.LimitHit).Inc()
+		// The log line names a byte limit's window with _bytes after it.
+		window, isBytes := strings.CutSuffix(line.LimitHit, "_bytes")
+
+		kind := ratelimit.KindRequests
+		if isBytes {
+			kind = ratelimit.KindBytes
+		}
+
+		m.rateLimitHits.WithLabelValues(window, kind).Inc()
 	}
 
 	if limit != "" {