The Core Rule Set, run by Coraza, on each request's method, URL and headers (closes #25)

Coraza v3.8.1 runs the Core Rule Set 4.25.0 (coraza-coreruleset v4.25.0)
after the rule files, with the six changes and the default
SWWAF_WAF_DISABLED_RULES that SPEC.md gives; no body, no response.
SWWAF_WAF_MODE, SWWAF_WAF_PARANOIA_LEVEL, SWWAF_WAF_ANOMALY_THRESHOLD and
SWWAF_WAF_EXEMPT_PATHS as specified; SWWAF_WAF_DISABLED_RULES refuses
900000 to 900999, smallwebwaf's own rules among them. A request with more
query parameters than Coraza reads, 1000, adds 5 (rule 900300). In block
mode a match is refused with 403, an offence counted toward the error
burst; in detect mode it is let through. Both log waf_rule_ids, waf_score
and duration_waf, raise waf_block, and count
smallwebwaf_waf_matches_total.

Judgement call: waf_block is raised in block mode too.
Deviation: no engine-error path; with no body read, Coraza cannot fail.

Model: opus-5-5

internal/waf/waf_test.go

@@ -139,7 +139,9 @@ func TestExpectAndContentEncodingAreAllowed(t *testing.T) {
 		request{http.MethodPost, push, []string{pushType, length, "Expect: 100-continue"}},
 		waf.Result{})
 	wantResult(t, crs,
-		request{http.MethodPost, fetch, []string{fetchType, length, "Content-Encoding: gzip"}},
+		request{http.MethodPost, fetch, []string{
+			fetchType, length, "Content-Encoding: gzip",
+		}},
 		waf.Result{})
 
 	// Every other header on the Core Rule Set's list stays refused.