Introduce a way to access the most recent response in User testing

[Mte90]

Ref: #4264
Ref: #4276

In the Pr I added a new variable in the user class to save the request with a method to return it.

[rodja]

Could you provide an example where the response would be helpful in testing?

[Mte90]

User cases:

• Check the request status, because you can have endpoints that are not avalaible in some cases or shouldn't be loaded by an user that doesn't have any permissions and check if there is something in page it means that is loading the page but not checking if the request happened. Basically is more fast and more readable in the code to check the status code instead if there is something in the page
• Check the request history (request.history) with the various redirects, can be used to check if the internal routing based on user permission as example works

[rodja]

Check the request status

Currently the user fixture asserts response code 200:

nicegui/nicegui/testing/user.py

Line 55 in 1137b50

assert response.status_code == 200, f'Expected status code 200, got {response.status_code}'

This would need to change if we want to check the request status codes.

Check the request history

This is tracked in #4281.

[Mte90]

I think that in tests we need to see if a user can open an endpoint, so maybe a parameter to open to set the status code to check maybe is an option.