The existing pattern of using `override_settings(MODULESTORE=...)` prevented
us from having more than one layer of subclassing in modulestore tests.

In a structure like:

    @override_settings(MODULESTORE=store_a)
    class BaseTestCase(ModuleStoreTestCase):
        def setUp(self):
            # use store

    @override_settings(MODULESTORE=store_b)
    class ChildTestCase(BaseTestCase):
        def setUp(self):
            # use store

In this case, the store actions performed in `BaseTestCase` on behalf of
`ChildTestCase` would still use `store_a`, even though the `ChildTestCase`
had specified to use `store_b`. This is because the `override_settings`
decorator would be the innermost wrapper around the `BaseTestCase.setUp` method,
no matter what `ChildTestCase` does.

To remedy this, we move the call to `override_settings` into the
`ModuleStoreTestCase.setUp` method, and use a cleanup to remove the override.
Subclasses can just defined the `MODULESTORE` class attribute to specify which
modulestore to use _for the entire `setUp` chain_.

[PLAT-419]

Refactoring the mocked user service object to return xblock user.

Invoice data model refactor

TNL-836

Assign regions/landmarks for easier navigation

Backfill course_modes migration

LMS Acceptance to one shard.

Add cosmetic price field to studio & logic

ECOM-891: Allow tracking of invoice transactions.

Authors: Awais Qureshi and Aamir Khan

- Price field added to Advanced Settings
- Function that decides which price to display
- Test added to check that the function outputs correct price
- Added feature flag and conditional to decide whether to display course price or not
- Feature Flag to show or hide course price on Course About page sidebar when not using shopping cart

Country access messaging theme fixup

Fixes broken answer and endorse icons on discussion forums

Revert "Add Cosmetic Display Price field to studio & logic to show it"

Move default country access messages out of static_templates, so they are not served by other Django views.

Fix a number of incorrect translation string uses.

These were found by the new pylint checker I wrote! :)

Add Cosmetic Display Price field to studio & logic to show it

Also cleaning up some lint.

This test consistently fails when combining
lms acceptance onto one shard. (TE-737)

We've transitioned many lettuce tests to bok-choy. It no longer
makes sense to keep LMS acceptance in two shards (each taking less
than 5 mins to run the actual tests).

ECOM-998: Country access messaging

Add new models to embargo to support country access

Use HTTP_X_FORWARDED_PROTO header in studio

disable PayAndVerifyTest.test_immediate_verification_enrollment

Add Django admin UI for configuring country access

Migrate existing embargo rules into the new tables.

Update translations (autogenerated message)

Introduce another bok-choy shard.