DEV: introduce `updateUrl` attribute to `theme-setting-editor` component.

app/assets/javascripts/admin/components/theme-setting-editor.js.es6

@@ -2,12 +2,14 @@ import Component from "@ember/component";
 import BufferedContent from "discourse/mixins/buffered-content";
 import SettingComponent from "admin/mixins/setting-component";
 import { ajax } from "discourse/lib/ajax";
+import { url } from "discourse/lib/computed";
 
 export default Component.extend(BufferedContent, SettingComponent, {
   layoutName: "admin/templates/components/site-setting",
+  updateUrl: url("model.id", "/admin/themes/%@/setting"),
 
   _save() {
-    return ajax(`/admin/themes/${this.model.id}/setting`, {
+    return ajax(this.updateUrl, {
       type: "PUT",
       data: {
         name: this.setting.setting,