Admin access controls

[WillGardella]

Implement access controls for all admin actions

[hsluoyz]

Hi, I'm the author of casbin. It is an authorization library that supports models like ACL, RBAC, ABAC.

Related to RBAC, casbin has several advantages:

1. roles can be cascaded, aka roles can have roles.
2. support resource roles, so users have their roles and resource have their roles too. role = group here.
3. the permission assignments (or policy in casbin's language) can be persisted in files or database.

So please consider using casbin when cbft implements access control security. Also let me know if there's any question:)