Rename internal/proxy to internal/servewaf (closes #173)

The package passes nothing to an app since rproxy took that over, so it
is named after the command it serves. Its constructor is New, like
rproxy's. The rproxy tests call their stand-in for servewaf standIn,
since a local servewaf would hide the package. No change of behaviour.

Model: opus-5-5

internal/servewaf/countries.go

@@ -0,0 +1,21 @@
+package servewaf
+
+import (
+	"slices"
+)
+
+// countryDenied reports whether the country lists refuse the request, by
+// the client's country as it was looked up. A client without a country,
+// or whose country cannot be found, is refused only by
+// SWWAF_EXCLUSIVELY_ALLOWED_COUNTRIES.
+func (rq *request) countryDenied() bool {
+	denied := rq.h.config.DeniedCountries
+	allowed := rq.h.config.ExclusivelyAllowedCountries
+	country := rq.line.Country
+
+	if slices.Contains(denied, country) {
+		return true
+	}
+
+	return len(allowed) > 0 && !slices.Contains(allowed, country)
+}