Task - RBAC AuthZ - Implement PoC permission and role for M0

[rodmgwgu]

Implement one role that grants a single permission, to validate enforcement and debug authorization behavior in isolation.

We could for example, implement a permission for the Advanced Settings section of course authoring, in that case, the following changes will be needed:

1. Define permission and role on openedx-authz
2. Modify endpoint in edx-platform so it validates for that permission (behind the feature flag)
3. Modify frontend-app-authoring to validate for that permission (and feature flag), and hide that menu item.