Refactor Setting (#3302)

* @object is not needed

* Remove unneeded dependencies

* Do not call private method

* Prefer #respond_to_missing? over #respond_to?

`#respond_to?` doesn't support `User.settings.method(:method_name)`

* Use find_or_initialize_by instead of

app/lib/settings/extend.rb

@@ -2,8 +2,6 @@
 
 module Settings
   module Extend
-    extend ActiveSupport::Concern
-
     def settings
       @settings ||= ScopedSettings.new(self)
     end

app/lib/settings/scoped_settings.rb

@@ -21,7 +21,7 @@ module Settings
     end
     # rubocop:enable Style/MethodMissing
 
-    def respond_to?(_method_name, _include_private = false)
+    def respond_to_missing?(*)
       true
     end
 
@@ -29,7 +29,7 @@ module Settings
       vars = thing_scoped
       records = vars.map { |r| [r.var, r] }.to_h
 
-      Setting.send(:default_settings).each do |key, default_value|
+      Setting.default_settings.each do |key, default_value|
         next if records.key?(key) || default_value.is_a?(Hash)
         records[key] = Setting.new(var: key, value: default_value)
       end
@@ -39,9 +39,8 @@ module Settings
 
     def []=(key, value)
       key = key.to_s
-      record = thing_scoped.find_by(var: key) || thing_scoped.new(var: key)
-      record.value = value
-      record.save!
+      record = thing_scoped.find_or_initialize_by(var: key)
+      record.update!(value: value)
 
       Rails.cache.write(Setting.cache_key(key, @object), value)
       value
@@ -51,11 +50,11 @@ module Settings
       Rails.cache.fetch(Setting.cache_key(key, @object)) do
         db_val = thing_scoped.find_by(var: key.to_s)
         if db_val
-          default_value = Setting.send(:default_settings)[key]
+          default_value = Setting.default_settings[key]
           return default_value.with_indifferent_access.merge!(db_val.value) if default_value.is_a?(Hash)
           db_val.value
         else
-          Setting.send(:default_settings)[key]
+          Setting.default_settings[key]
         end
       end
     end

app/models/setting.rb

@@ -23,7 +23,7 @@ class Setting < RailsSettings::Base
     def [](key)
       return super(key) unless rails_initialized?
 
-      val = Rails.cache.fetch(cache_key(key, @object)) do
+      val = Rails.cache.fetch(cache_key(key, nil)) do
         db_val = object(key)
 
         if db_val
@@ -50,8 +50,6 @@ class Setting < RailsSettings::Base
       records
     end
 
-    private
-
     def default_settings
       return {} unless RailsSettings::Default.enabled?
       RailsSettings::Default.instance