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/dsl.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module UserSettings::DSL
+  module ClassMethods
+    def setting(key, options = {})
+      @definitions ||= {}
+
+      UserSettings::Setting.new(key, options).tap do |s|
+        @definitions[s.key] = s
+      end
+    end
+
+    def namespace(key, &block)
+      @definitions ||= {}
+
+      UserSettings::Namespace.new(key).configure(&block).tap do |n|
+        @definitions.merge!(n.definitions)
+      end
+    end
+
+    def keys
+      @definitions.keys
+    end
+
+    def definition_for(key)
+      @definitions[key.to_sym]
+    end
+
+    def definition_for?(key)
+      @definitions.key?(key.to_sym)
+    end
+  end
+
+  def self.included(base)
+    base.extend ClassMethods
+  end
+end