FIX: Don't store translated trust level names in anonymous cache (#13224)

Refactors `TrustLevel` and moves translations from server to client

Additional changes:
  * "staff" and "admin" wasn't translatable in site settings
  * it replaces a concatenated string with a translation
  * uses translation for trust levels in users_by_trust_level report
  * adds a DB migration to rename keys of translation overrides affected by this commit

app/models/concerns/reports/users_by_trust_level.rb

@@ -24,7 +24,7 @@ module Reports::UsersByTrustLevel
       ]
 
       User.real.group('trust_level').count.sort.each do |level, count|
-        key = TrustLevel.levels[level.to_i]
+        key = TrustLevel.name(level.to_i)
         url = Proc.new { |k| "/admin/users/list/#{k}" }
         report.data << { url: url.call(key), key: key, x: level.to_i, y: count }
       end

app/models/site.rb

@@ -21,7 +21,7 @@ class Site
   end
 
   def trust_levels
-    TrustLevel.all
+    TrustLevel.levels
   end
 
   def user_fields

app/models/trust_level_and_staff_setting.rb

@@ -18,4 +18,12 @@ class TrustLevelAndStaffSetting < TrustLevelSetting
   def self.special_groups
     ['staff', 'admin']
   end
+
+  def self.translation(value)
+    if special_group?(value)
+      I18n.t("trust_levels.#{value}")
+    else
+      super
+    end
+  end
 end

app/models/trust_level_setting.rb

@@ -8,18 +8,23 @@ class TrustLevelSetting < EnumSiteSetting
   end
 
   def self.values
-    levels = TrustLevel.all
-    valid_values.map { |x|
-      {
-        name: x.is_a?(Integer) ? "#{x}: #{levels[x.to_i].name}" : x,
-        value: x
-      }
-    }
+    valid_values.map do |value|
+      { name: translation(value), value: value }
+    end
   end
 
   def self.valid_values
     TrustLevel.valid_range.to_a
   end
 
+  def self.translation(value)
+    I18n.t(
+      "js.trust_levels.detailed_name",
+      level: value,
+      name: TrustLevel.name(value)
+    )
+  end
+
   private_class_method :valid_values
+  private_class_method :translation
 end