Core Rule Set: Forgejo's ordinary requests pass by default (closes #342)

Forgejo 17.0.1's recorded requests are in
testdata/forgejo-requests.txt, checked at the defaults.

What Forgejo sends and gitea does not:
- its flash cookie is named flash, which joins gitea_flash among the
  cookies left out;
- its wiki search, whose q skips five rules in forgejo.conf, the
  fifteenth change.

Gaps in gitea's fixes the recording showed: q on the name searches
skips 932250 (ls -la), and the API's package search is one of them.
User and organisation pages, any one-segment path, keep 932250.

Model: opus-5-5

internal/coreruleset/coreruleset.go

@@ -1,6 +1,6 @@
 // Package coreruleset runs the OWASP Core Rule Set 4.25.0, through Coraza, on the
 // method, the URL with its query and the headers of a request, and on its
-// body while SWW_WAF_BODY_LIMIT is set, with the fourteen changes sww
+// body while SWW_WAF_BODY_LIMIT is set, with the fifteen changes sww
 // makes to it and the exclusions in SWW_CORE_RULE_SET_EXCLUSIONS_FILE, as
 // "Attack detection" under "Settings" in SPEC.md describes them. It reads no
 // response.
@@ -36,7 +36,7 @@ import (
 // giteaExclusions for the third, wordpressExclusions for the fourth,
 // drupalExclusions for the fifth, mediawikiExclusions for the sixth,
 // mastodonExclusions for the seventh, vaultwardenExclusions for the eighth,
-// and nextcloudExclusions for the ninth.
+// nextcloudExclusions for the ninth, and forgejoExclusions for the tenth.
 // Each rule sww adds has an id from 900000 to 900999, the ids the
 // Core Rule Set keeps for the rules that set it up, which
 // SWW_WAF_DISABLED_RULES and the exclusions file refuse, so that no
@@ -102,7 +102,10 @@ SecRule ARGUMENTS_LIMIT_REACHED "@eq 1" "id:900300,phase:2,pass,\
 # So does the thirteenth.
 %s
 
-# And the fourteenth.
+# So does the fourteenth.
+%s
+
+# And the fifteenth.
 %s
 
 # The sixth: only the rules for requests are loaded, and no response is
@@ -239,11 +242,19 @@ var vaultwardenExclusions string
 //go:embed nextcloud.conf
 var nextcloudExclusions string
 
+// forgejoExclusions are the fifteenth change: the fields of Forgejo's own
+// requests that skip the rules that refused them there, where Forgejo differs
+// from gitea, as Coraza directives.
+//
+//go:embed forgejo.conf
+var forgejoExclusions string
+
 // cookiesNotRead are the cookies the Core Rule Set reads a request
-// without, the rest of the fifth change.
+// without, the rest of the fifth change. flash is Forgejo's name for
+// gitea_flash.
 //
 //nolint:gochecknoglobals // a constant cannot be a list
-var cookiesNotRead = []string{"gitea_flash", "redirect_to"}
+var cookiesNotRead = []string{"gitea_flash", "flash", "redirect_to"}
 
 // Params are what New needs.
 type Params struct {
@@ -352,7 +363,7 @@ type CoreRuleSet struct {
 	bodyLimit int64
 }
 
-// New returns the Core Rule Set with the fourteen changes, at params'
+// New returns the Core Rule Set with the fifteen changes, at params'
 // paranoia level, without the rules it switches off, reading request
 // bodies up to params' limit, and with params' exclusions file loaded
 // before the Core Rule Set's rules. An exclusions file is an error if it
@@ -382,7 +393,7 @@ func New(params Params) (*CoreRuleSet, error) {
 	text := fmt.Sprintf(directives, params.ParanoiaLevel, body, exclusions,
 		giteaExclusions, wordpressExclusions, drupalExclusions,
 		mediawikiExclusions, mastodonExclusions, vaultwardenExclusions,
-		nextcloudExclusions)
+		nextcloudExclusions, forgejoExclusions)
 
 	if len(params.DisabledRules) > 0 {
 		ids := make([]string, len(params.DisabledRules))