Change user settings to be stored in a more optimal way (#23630)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/models/user_settings/namespace.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class UserSettings::Namespace
+  attr_reader :name, :definitions
+
+  def initialize(name)
+    @name        = name.to_sym
+    @definitions = {}
+  end
+
+  def configure(&block)
+    instance_eval(&block)
+    self
+  end
+
+  def setting(key, options = {})
+    UserSettings::Setting.new(key, options.merge(namespace: name)).tap do |s|
+      @definitions[s.key] = s
+    end
+  end
+end