Task - RBAC AuthZ - Modify Advanced Settings endpoint for PoC

[rodmgwgu]

See openedx/openedx-authz#185

Advanced Settings related endpoint:

GET /api/contentstore/v0/advanced_settings/(courseid)/: Get advanced settings

PATCH /api/contentstore/v0/advanced_settings/(courseid)/: Update advanced settings

GET /api/contentstore/v1/proctoring_errors/(courseid)/: Get info on proctoring errors

[rodmgwgu]

Daniel's idea: explore defining a decorator for permission cheching