Request tags, with refusing and limits per tag (closes #175)

Each request gets sorted tags from the lookup, new address lists, the
reputation sources and the rule matches, logged as `tags`. New settings:
`SWW_TAG_LISTS`, `SWW_TAG_DENY`, `SWW_TAG_LIMIT_PERCENT`. They replace
`SWW_ASN_LIMIT_PERCENT`, `SWW_COUNTRY_LIMIT_PERCENT` and
`SWW_DENIED_COUNTRIES`. New heuristics `tag_lists` and `tag_deny`; the
latter runs before the rate limits and again after the Core Rule Set.

Model: opus-5-5

internal/discriminator/heuristics.go

@@ -43,12 +43,15 @@ const (
 // country are looked up, so that a client they refuse is not looked up.
 func beforeLookup() []heuristic {
 	return []heuristic{
+		tagLists{},
 		denyNets{},
 		activeBan{},
 	}
 }
 
 // afterLookup are the heuristics that run once the lookup has been made.
+// tag_deny runs twice: before the rate limits, on the tags known by then, and
+// last, on the tag rule_files and core_rule_set can add.
 func afterLookup() []heuristic {
 	return []heuristic{
 		countries{},
@@ -56,11 +59,13 @@ func afterLookup() []heuristic {
 		crowdSec{},
 		dnsbl{},
 		abuseIPDB{},
+		tagDeny{},
 		rateLimits{},
 		trapPaths{},
 		ruleFiles{},
 		headerLimits{},
 		coreRuleSet{},
+		tagDeny{},
 	}
 }