Task - RBAC AuthZ - Implement new permissions for group configurations

[rodmgwgu]

Implement new permissions for group configurations.

Should live behind the feature flag.

Relevant permission:

courses.manage_group_configurations

Changes needed:

edx-platform: implement permission checks on endpoint handler behind flag

Endpoints:

GET /api/contentstore/v1/group_configurations/(courseid)/: Get group configurations
POST /group_configurations/(courseid)/(configurationid)/: Edit group
POST /group_configurations/(courseid)/(configurationid)/: Create new group
DELETE /group_configurations/(courseid)/(configurationid)/(itemid)/: Delete group

Reference implementation: https://github.com/openedx/openedx-platform/pull/38009/changes