LEARNER-2307

Modified how the per object permissions are enforced in the CCX REST APIs

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

The permissions class now supports non-GET requests.

ECOM-2893

- The permission now checks the correct request attribute (GET instead of data).
- The Credit API view test has been updated to check for the positive access instead of just denial.

 ECOM-3096

- API built atop Django REST Framework
- Added support for OAuth 2.0 and session authentication
- Added permissions around eligibility data

ECOM-2609

* Fix paver violations to stablize edx-lint update
* Parens, Line2Long
* Fix missing docstrings
* Fix PEP8 issues
* Address PR feedback (thanks @nedbat!)

IsAuthenticatedOrDebug hides potential issues with API client code that is run in local environments and later deployed to production where authentication fails.

XCOM-193

TNL-1537

Co-Authored-By: Andy Armstrong <andya@edx.org>
Co-Authored-By: cahrens <christina@edx.org>

TNL-1493

See https://openedx.atlassian.net/wiki/display/TNL/User+API for details

XCOM-107