feat(users): validate usernames before creating or renaming (#610)

tests/unit/utils/user.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, test } from "vitest";
 
 import type { User } from "~/types/User";
-import { getUserDisplayName } from "~/utils/user";
+import { getUserDisplayName, USERNAME_PATTERN, validateUsername } from "~/utils/user";
 
 const makeUser = (overrides: Partial<User>): User => ({
   id: "default-id",
@@ -56,3 +56,30 @@ describe("getUserDisplayName", () => {
     expect(getUserDisplayName(user)).toBe("John Doe");
   });
 });
+
+describe("validateUsername", () => {
+  test.each(["ab", "john_doe", "user-1.name", "alice@example.com", "josé"])(
+    "accepts %s",
+    (name) => {
+      expect(validateUsername(name)).toBeUndefined();
+    },
+  );
+
+  // "lm@" is the case from #502: Headscale creates it, but policies strip the
+  // trailing "@" so no rule can ever match the user.
+  // `ab²`/`abⅫ` are Nl/No, which Go's unicode.IsDigit rejects.
+  test.each(["", "a", "1abc", "@abc", "lm@", "a@b@c", "bad name", "bad/name", "ab²", "abⅫ"])(
+    "rejects %s",
+    (name) => {
+      expect(validateUsername(name)).toBeTypeOf("string");
+    },
+  );
+});
+
+describe("USERNAME_PATTERN", () => {
+  test("is a valid HTML pattern (unicode sets mode)", () => {
+    const regex = new RegExp(`^${USERNAME_PATTERN}$`, "v");
+    expect(regex.test("alice@example.com")).toBe(true);
+    expect(regex.test("lm@")).toBe(false);
+  });
+});