Reject dot-only usernames (#24611)

* reject usernames made only of dots

A username of "." or ".." passed validation, but browsers resolve those as path segments, so requests to /users/{username} never reached the API and the user could not be deleted or edited from the UI. User creation now rejects dot-only names in both the API and the create user dialog.

* show a specific error for dot-only usernames

Entering "." or ".." in the create user dialog showed the message listing periods as allowed characters, which didn't explain the rejection. The dialog now checks for dot-only names separately and shows its own message.

frigate/test/http_api/test_http_users.py

@@ -0,0 +1,33 @@
+"""Tests for user creation."""
+
+from unittest.mock import MagicMock
+
+from frigate.models import User
+from frigate.test.http_api.base_http_test import AuthTestClient, BaseTestHttp
+
+PASSWORD = "a-valid-password-123"
+
+
+class TestCreateUser(BaseTestHttp):
+    def setUp(self):
+        super().setUp([User])
+        self.app = super().create_app()
+        self.app.config_publisher = MagicMock()
+
+    def _create(self, username: str):
+        with AuthTestClient(self.app) as client:
+            return client.post(
+                "/users",
+                json={"username": username, "password": PASSWORD, "role": "viewer"},
+            )
+
+    def test_rejects_dot_only_usernames(self):
+        # browsers resolve these as URL path segments, so the per-user
+        # endpoints can never be reached for them
+        for username in (".", "..", "..."):
+            assert self._create(username).status_code == 400
+            assert User.get_or_none(User.username == username) is None
+
+    def test_accepts_username_containing_dots(self):
+        assert self._create("john.doe_1").status_code == 200
+        assert User.get_or_none(User.username == "john.doe_1") is not None