DEV: Update admin modal controllers to native class syntax (#20685)

This commit was generated using the ember-native-class-codemod along with a handful of manual updates

app/assets/javascripts/admin/addon/controllers/modals/admin-merge-users-confirmation.js

@@ -1,18 +1,21 @@
+import { alias } from "@ember/object/computed";
 import Controller, { inject as controller } from "@ember/controller";
 import I18n from "I18n";
 import ModalFunctionality from "discourse/mixins/modal-functionality";
 import { action } from "@ember/object";
-import { alias } from "@ember/object/computed";
 import discourseComputed from "discourse-common/utils/decorators";
 
-export default Controller.extend(ModalFunctionality, {
-  adminUserIndex: controller(),
-  username: alias("model.username"),
-  targetUsername: alias("model.targetUsername"),
+export default class AdminMergeUsersConfirmationController extends Controller.extend(
+  ModalFunctionality
+) {
+  @controller adminUserIndex;
+
+  @alias("model.username") username;
+  @alias("model.targetUsername") targetUsername;
 
   onShow() {
     this.set("value", null);
-  },
+  }
 
   @discourseComputed("username", "targetUsername")
   text(username, targetUsername) {
@@ -20,28 +23,28 @@ export default Controller.extend(ModalFunctionality, {
       username,
       targetUsername,
     });
-  },
+  }
 
   @discourseComputed("username")
   mergeButtonText(username) {
     return I18n.t(`admin.user.merge.confirmation.transfer_and_delete`, {
       username,
     });
-  },
+  }
 
   @discourseComputed("value", "text")
   mergeDisabled(value, text) {
     return !value || text !== value;
-  },
+  }
 
   @action
   confirm() {
     this.adminUserIndex.send("merge", this.targetUsername);
     this.send("closeModal");
-  },
+  }
 
   @action
   close() {
     this.send("closeModal");
-  },
-});
+  }
+}