waf: the header limits are the first check (closes #311)

A request over 50 cookies or 100 header fields is now refused by the first
check after SWW_ALLOW_NETS. It causes no lookup, no query to RouteWatch, a DNS
blocklist or AbuseIPDB, no rule file match and no Core Rule Set. The rate
limits no longer count it, and a banned or denied client gets 431 for it. It
makes no ban, makes no ban permanent and is not counted in a ban's notes. In
observe mode no lookup is made for it. Requests within the limits go through
the same checks in the same order.

Model: opus-5-5

internal/waf/waf.go

@@ -143,10 +143,9 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 
 // refusedWhateverTheAnswer reports whether the request is one that does not wait
 // for GeoJS, since the checks will refuse it at now whatever GeoJS answers about
-// its client: the heuristic crowdsec, header_limits, blocklists or rate_limits
-// will refuse it, as a function in that heuristic's file says. In observe mode,
-// which refuses nothing, none is. rproxy lets a request through when
-// waf answers too late.
+// its client: the heuristic crowdsec, blocklists or rate_limits will refuse it,
+// as a function in that heuristic's file says. In observe mode, which refuses
+// nothing, none is. rproxy lets a request through when waf answers too late.
 func (rq *request) refusedWhateverTheAnswer(now time.Time) bool {
 	if rq.h.config.Observe {
 		return false
@@ -154,8 +153,7 @@ func (rq *request) refusedWhateverTheAnswer(now time.Time) bool {
 
 	_, decided := rq.crowdSecDecisionInForce(now)
 
-	return decided || overHeaderLimits(rq.headerCounts()) ||
-		rq.refusedByBlocklists(rq.h.lists.ListedBy(rq.client)) ||
+	return decided || rq.refusedByBlocklists(rq.h.lists.ListedBy(rq.client)) ||
 		rq.overAWholeRateLimit(now)
 }