Also fix "is_anonymous" attribute value in WebTestCase subclass.

Co-authored-by: Basil Dubyk <samitnuk.work@gmail.com>
Co-authored-by: Alexander Gaevsky <sasha@sasha0.ru>
Co-authored-by: Joseph Wayodi <jwayodi@gmail.com>

Fixes #3258.

Non-exclusive offers that only allow combination with specific other offers

Fix handling of count conditions in `MultibuyDiscountBenefit`

Switch to using freezegun for tests that depend on date.

... because the basket flow also ignores them.

When looking up a URL for a forked app, the previous mechanism fetched the top level AppConfig which allows every user.
The new mechanism creates a dict of dashboard URLs/configs and does a lookup to find a DashboardConfig.

This will also raise NoReverseMatch if the URL does not exist or is not a dashboard URL.

fix https://github.com/django-oscar/django-oscar/issues/3080

We aren't changing `label` or `verbose_name` so let's use class inheritance instead

ref https://github.com/django-oscar/django-oscar/issues/3080

* Retrieving product options now performs only 1 query.

Also it returns all the product options combined. This makes more sense because
as the existing tests prove, there is already a way to retrieve the product_class
options and the product options separately.

* Implement basic abstract thumbnails generator backend

* Create `oscar_thumbnail` template tag in `image_tags`

* Add `easy_thumbnails` to `INSTALLED_APPS` in sandbox settings

* Modify `primary_image` method of `Product` model

* Override in templates Sorl's `thumbnail` tag with `oscar_thumbnail` tag

* Check that related module is installed during thumbnail class initialization

* Add params to `original` field of `ProductImageFactory`

* Add media related URLs to test settings

* Add unit tests for thumbnailer backend

* Create test helpers in `test/utils`

These helpers will be used in tests related to thumbnails

* Add tests to check `oscar_thumbnail` template tag

* Add test to check images/thumbnails deleted for deleted product

* Move `sorl-thumbnail` and `easy-thumbnails` to `extras_require`

With this change these packages can be installed as
* `pip install django-oscar[sorl-thumbnail]`
* `pip install django-oscar[easy-thumbnails]`

* Updated "Template tags" section in docs with info about `oscar_thumbnail`

* Describe `OSCAR_THUMBNAILER` setting in "Settings" section of the docs

* Add information about created thumbnail backend to the release notes

This change will allow to import `run_concurrently` helper for test
purposes in other libraries.

* enforce max_affected_items during offer application

also restrict the usage of offer consumption to line.consume()

* improve test coverage