feat: sitemap settings singleton with content types and additional addresses

- one settings tile opening the golem15.sitemap.settings singleton
- Files tab (site address, file size, S1 files partial), Additional
  addresses repeater, Content types tab built from signpost at boot
- golem15_sitemap_types; a type switched off leaves the files (reason type)
- a save validates (errors.*) and dispatches a rebuild after commit

classes/types.go

@@ -0,0 +1,54 @@
+package classes
+
+import (
+	"git.golem15.com/golem15/sm-sitemap-plugin/models"
+	"git.golem15.com/golem15/summercms/modules/pact"
+	"gorm.io/gorm"
+)
+
+// ReservedSlugs are file name parts no content type may use: the image
+// and News sitemaps own them.
+var ReservedSlugs = map[string]bool{"images": true, "news": true}
+
+// TypeConfig is a content type's effective sitemap setting: its key and
+// label, whether its records are listed, its group slug and its HTML
+// sitemap headings (nil when none was saved).
+type TypeConfig struct {
+	Key     string
+	Label   string
+	Include bool
+	Slug    string
+	Titles  map[string]string
+}
+
+// LoadTypeSettings reads the saved content type settings by type key.
+func LoadTypeSettings(db *gorm.DB) (map[string]models.TypeSetting, error) {
+	var rows []models.TypeSetting
+	if err := db.Find(&rows).Error; err != nil {
+		return nil, err
+	}
+	out := make(map[string]models.TypeSetting, len(rows))
+	for _, r := range rows {
+		out[r.TypeKey] = r
+	}
+	return out, nil
+}
+
+// EffectiveType is the setting of typ: the saved row, else listed under
+// DefaultSlug. A saved slug that is not a ValidSlug falls back to the
+// default.
+func EffectiveType(typ pact.MenuItemType, rows map[string]models.TypeSetting) TypeConfig {
+	cfg := TypeConfig{Key: typ.Key, Label: typ.Label, Include: true, Slug: DefaultSlug(typ.Key)}
+	row, ok := rows[typ.Key]
+	if !ok {
+		return cfg
+	}
+	cfg.Include = row.Include
+	if ValidSlug(row.Slug) {
+		cfg.Slug = row.Slug
+	}
+	if titles := row.Titles.Get(); len(titles) > 0 {
+		cfg.Titles = titles
+	}
+	return cfg
+}