[Feature] Override global settings (#9718)

* Provide mechanism for config to override global settings

* Ensure overrides are observed on save

* Refactor

* Add "read_only" field to serializer

* Prevent editing for read_only settings

* Bump API version

* Update docs

* Secure logs

* Override applies to default_value

* override get_setting method

* Add unit test

* Utilize new approach to override SITE_URL

* Docs updates

* Docs tweaks

* Shortcut for get_global_setting

* Remove previous change

- Allow validation to be performed within the InvenTreeSetting class

* Override INVENTREE_BASE_URL setting

* Handle error on worker boot

* Tweak unit test

src/frontend/lib/types/Settings.tsx

@@ -33,6 +33,7 @@ export interface Setting {
   plugin?: string;
   method?: string;
   required?: boolean;
+  read_only?: boolean;
 }
 
 export interface SettingChoice {