TNL-5990

Discussion is restricted to the CCX course (there is no sharing of
discussions with the parent course or other CCX instances).

Adds ENABLE_SUBSECTION_GRADES_SAVED feature flag to both lms and cms. Also
installs the wiring that will allow robust grades to be used for courses
that enable it. This functionality is still gated by the feature flag
and should not be used until the remaining robust grades work is finished.

By default, disable all caching in tests, to preserve test independence.
In order to enable caching, inherit from CacheSetupMixin, and specify
which cache configuration is needed.

[EV-32]

MA-2258

MA-2258

Added validation to ccx create form, If ccxcon url is set then app will ask user to create ccx from ccxcon app

This reverts commit acf6c1d6, reversing
changes made to c59db6e5.

Revert "Added staff role on ccx to staff of master course and added a data migration for existing ccx courses."

This reverts commit 91bf48fc.

Before it was depending on the order of results, which is not very consistent.  Now we use known identifiers to delve through data before making our assertions.

Added staff role on ccx to staff of master course and added a data migration for existing ccx courses.

We added the ability here to check if a role has a user in with the ability to refresh the role cache before checking.  Since some tests will make inline requests, which in turn put a user into a new role, we have to refresh afterwards otherwise we won't see that new role in place.  Since we don't want to automatically refresh ever, we just added a way to request it, since we know in this test that we're doing something, effectively, out-of-band, which necessitates it.

CCX REST APIs
OAUTH2 authorization for CCX APIs
- oauth2 authorization required for ccx list.
- Course-instructor permission for ccx api endpoint
- Protection for detail view too.

Tests for CCX REST APIs and OAUTH2 authorization

CCX overrides course max_student_enrollments_allowed
and set it to 200 during CCX creation

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

Make the course URL pattern more generic.

Comment newly added functionality.

Fix quality issues.

Address two lint errors, with regex and variable naming.

Changed how we access course_key and course_id.

Replace another instance of self.course.id.to_deprecated_string()

Remove unused import, add missing one.

Improve how the ccx key is extracted from the URL

Use resolve() instead of os.path to get the course_id.

Remove the granting of staff access to coaches.

In the CCX dashboard, the Student Admin tab has a `Download student
grades` action. This action should download a CSV file containing
grades, but currently displays the CSV content in the browser instead.
This fix sets the `content-type` and `content-disposition` so that
a CSV file download occurs.

- fixes #93

If a block is marked as "hide from students" cannot be seen in the
CCX schedule