Admin-readonly-role

At the Juno Operator's mid-cycle meetup there was a request for users with admin-readonly privileges.

Excerpting from https://etherpad.openstack.org/p/SAT-ops-security the role related interchange.

•	Tenants, roles, user creation etc
 * roles right now are either all pervasive super admin or end user. Having multiple roles are not uniformly supported, for instance glance
 * lack of usable RBAC for admin: either admin, or nothing
 * and, to make it worse, static configs as management of capabilities
 * some hardcoded in code assumptions that you must be admin to do X


 * also related: difficulty in knowing what can be configured
 * Congress as a proposed solution

•	does anyone have >2 roles?
 * yes 3 level roles - god / tenant admin / user - users can't alter other user's stuff. However, glance does not support this at all: images are owned by the tenant_id, so anyone else in the tenant can delete/alter it
 * glance owner_is_tenant - doesn't appear to be well tested.
 * option: use repose to fake RBAC on top of the API that doesn't support
 * We use 5 roles but in practice, only 4 of those are valid and only god/user have anything to do with real privs. (We use one extra role to allow/disallow DELETION of floating ip assignment which is arguably a specific level of control/role.)