fix(17): T-17-15 refuse an unsafe frontend_url on save and import

- Settings.BeforeValidate answers a cabana validation error on
  frontend_url, so the settings save is a 422 and the row is unchanged
- sitemap:import-winter stops on a frontend_url that
  models.AllowedFrontendURL refuses, before the dry-run branch and before
  any database use; the value is printed quoted
- errors.frontend_url phrase in en and pl
- TestSettingsBeforeValidate, TestWinterSettingsFrontendURL and the save
  and import refusals in the Postgres smokes

models/settings.go

@@ -5,8 +5,14 @@ import (
 	"strings"
 	"unicode"
 	"unicode/utf8"
+
+	"git.golem15.com/golem15/summercms/modules/cabana"
+	"gorm.io/gorm"
 )
 
+// errFrontendURL is the phrase key of the frontend_url refusal.
+const errFrontendURL = "golem15.sitemap::lang.errors.frontend_url"
+
 // The settings keys of the five priority tiers, in the order PHP checked
 // them. A tier rule names one of them.
 const (
@@ -34,6 +40,8 @@ var PriorityDefaults = map[string]string{
 // UpdatesManifestPath names a JSON file of URL path to last-modified date;
 // EnablePriorityTiers turns the tier priorities on, and the priority fields
 // hold each tier's value as text. A null priority reads as its PHP default.
+// The PHP settings form validated nothing; the port checks FrontendURL in
+// BeforeValidate.
 type Settings struct {
 	ID                    uint    `gorm:"column:id;primaryKey"`
 	FrontendURL           *string `gorm:"column:frontend_url"`
@@ -58,9 +66,21 @@ func (Settings) Fillable() []string {
 	}
 }
 
-// Rules is empty: the PHP settings form validated nothing.
+// Rules is empty: the PHP settings form validated nothing. The one check of
+// the port, on frontend_url, is in BeforeValidate.
 func (Settings) Rules() map[string]string { return map[string]string{} }
 
+// BeforeValidate is the lagoon.HasBeforeValidate hook cabana calls on a
+// settings save, after the fill and before the row is written: a
+// frontend_url that AllowedFrontendURL refuses is a validation error on
+// frontend_url, so the save answers 422 and the row is left as it was.
+func (s Settings) BeforeValidate(*gorm.DB) error {
+	if AllowedFrontendURL(Text(s.FrontendURL)) {
+		return nil
+	}
+	return &cabana.ValidationError{Details: map[string]any{"frontend_url": []string{errFrontendURL}}}
+}
+
 // AllowedFrontendURL reports whether u may be the frontend_url setting: the
 // empty string, or an absolute http or https URL with a host and without
 // whitespace, control characters, a double quote, <, > or &. The PHP plugin