### Description

https://github.com/apache/airflow/pull/17946 implements a `/robots.txt` endpoint to block search engines crawling Airflow - in the cases where it is (accidentally) exposed to the public Internet.

If we record any GET requests to that end-point we'd have a strong warning flag that the deployment is exposed, and could issue a warning in the UI, or even enable some kill-switch on the deployment. 

Some deployments are likely intentionally available and rely on auth mechanisms on the `login` endpoint, so there should be a config option to suppress the warnings.

An alternative approach would be to monitor for requests from specific user-agents used by crawlers for the same reasons

### Use case/motivation

People who accidentally expose airflow have a slightly higher chance of realising they've done so and tighten their security.

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

tests/www/views/test_views_base.py
resp = admin_client.post(
        "users/add",
        data={
            'first_name': 'fake_first_name',
            'last_name': 'fake_last_name',
            'username': non_exist_username,
            'email': 'fake_email@email.com',
            'password': 'test',
            'conf_password': 'test',
        },
        follow_redirects=True,
    )
    check_content_in_response("Added Row", resp)
    assert app.appbuilder.sm.find_user(non_exist_username)
@pytest.fixture()
def exist_username(app, exist_role):
    username = "test_edit_user_user"
    app.appbuilder.sm.add_user(
        username,
        "first_name",
        "last_name",
        "email@email.com",
        exist_role,
        password="password",
    )
    yield username
    if app.appbuilder.sm.find_user(username):
        app.appbuilder.sm.del_register_user(username)
def test_edit_user(app, admin_client, exist_username):