fix: Freeze core Request fields

[Mantisus]

Description

• Ensures that core Request fields such as unique_key, method, and others will not be changed.

[vdusek]

I agree in principle, but I'm not entirely sure we can do it. We should definitely test this change on the platform - run integration and E2E tests in the SDK.

[janbuchar]

I agree in principle, but I'm not entirely sure we can do it. We should definitely test this change on the platform - run integration and E2E tests in the SDK.

I completely agree with this. I don't see a good reason why it shouldn't work, but better safe than sorry.

Once this is ready, no need to wait for my review unless you decide to change the PR substantially.

[Pijukatel]

I can not start the E2E tests directly on the branch from forked repo. I created a copy of the branch and started the tests here: https://github.com/apify/crawlee-python/actions/runs/20028369926

[vdusek]

tests in the SDK - https://github.com/apify/apify-sdk-python/actions/runs/20029622226/job/57435192024?pr=702

Edit: they're failing

[vdusek]

Also do we want to freeze only these 4 fields?

List of all from docs:

What about label, max_retries, no_retry, enqueue_strategy, forefront?