Refactor tests for RedirectUrlResolver class
Refactor tests for RedirectUrlResolver class

The refactoring introduces two new classes: HeadSideEffects
and ResolveRedirectsSideEffects. They are intended to store data related to
setup of mocks of requests.Session.head and requests.Session.resolve_redirects,
injected into RedirectUrlResolver for testing.

RedirectUrlResolverTest class is being refactored to make use of these new classes.
_response_mocks property and _set_up_resolve_redirects and
_set_last_location_header methods are being removed, and _set_up_side_effects
method is being added. The remaining methods are being refactored
to accommodate for these changes.

piotr-rusin/spam-lists