add public suffix support, remove 2 underscores from txt

apps/builder/app/builder/features/topbar/cname.test.ts

@@ -0,0 +1,39 @@
+import { describe, test, expect } from "@jest/globals";
+
+import { extractCname } from "./cname";
+
+describe("extractCname from ordinary domains", () => {
+  test('should return "@" for top level like domains', () => {
+    expect(extractCname("example")).toBe("@");
+  });
+
+  test('should return "@" for root level domains', () => {
+    expect(extractCname("example.com")).toBe("@");
+  });
+
+  test("should return the subdomain", () => {
+    expect(extractCname("sub.example.com")).toBe("sub");
+  });
+
+  test("should return all subdomains", () => {
+    expect(extractCname("sub.sub.example.com")).toBe("sub.sub");
+  });
+});
+
+describe("extractCname from public suffix domains", () => {
+  test('should return "@"', () => {
+    expect(extractCname("co.za")).toBe("@");
+  });
+
+  test('should return "@"', () => {
+    expect(extractCname("example.co.za")).toBe("@");
+  });
+
+  test("should return all the subdomain", () => {
+    expect(extractCname("sub.example.co.za")).toBe("sub");
+  });
+
+  test("should handle domains with multiple public suffixes correctly", () => {
+    expect(extractCname("sub.sub.example.co.za")).toBe("sub.sub");
+  });
+});