FEATURE: admin UI to merge two users. (#9509)

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

@@ -0,0 +1,35 @@
+import Controller, { inject as controller } from "@ember/controller";
+import ModalFunctionality from "discourse/mixins/modal-functionality";
+import discourseComputed from "discourse-common/utils/decorators";
+import { alias } from "@ember/object/computed";
+
+export default Controller.extend(ModalFunctionality, {
+  adminUserIndex: controller(),
+  username: alias("model.username"),
+  targetUsername: alias("model.targetUsername"),
+
+  onShow() {
+    this.set("value", null);
+  },
+
+  @discourseComputed("username", "targetUsername")
+  text(username, targetUsername) {
+    return `transfer @${username} to @${targetUsername}`;
+  },
+
+  @discourseComputed("value", "text")
+  mergeDisabled(value, text) {
+    return !value || text !== value;
+  },
+
+  actions: {
+    merge() {
+      this.adminUserIndex.send("merge", this.targetUsername);
+      this.send("closeModal");
+    },
+
+    cancel() {
+      this.send("closeModal");
+    }
+  }
+});