Enforce granular role-based access control for user functions

Enforce granular role-based access control for user functions:

	Cluster User	Service Operator	Service Administrator	Cluster Operator	Cluster Administrator	Administrator
Create new clusters
Manage users
Assign permissions/roles

Entry points affected:

• GET /api/v1/users/:username
• GET /api/v1/users/:username/widget_layouts
• GET /api/v1/users/:username/privileges
• POST /api/v1/users/:username
• DELETE /api/v1/users/:username
• PUT /api/v1/users/:username
• GET /api/v1/priviliges
• POST /api/v1/priviliges
• GET /api/v1/priviliges/:privilege_id
• DELETE /api/v1/priviliges/:privilege_id
• PUT /api/v1/priviliges/:privilege_id
• GET /api/v1/clusters/:cluster_name/priviliges
• GET /api/v1/clusters/:cluster_name/priviliges/:privilege_id
• POST /api/v1/clusters/:cluster_name/priviliges
• DELETE /api/v1/clusters/:cluster_name/priviliges/:privilege_id
• PUT /api/v1/clusters/:cluster_name/priviliges/:privilege_id