Split “Using RBAC Authorization” into concept / reference / task pages

[sftim]

This is a Feature Request

What would you like to be added
Update the content on https://kubernetes.io/docs/reference/access-authn-authz/rbac/ to new pages:

• a new concept page inside https://kubernetes.io/docs/concepts/security/
• new task pages
  • assigning default roles
    For this task, say that it is assumed the user is a cluster administrator.
    For this task, say it is assumed that cluster is already configured to use RBAC. Point to "Setting up RBAC" Task for users missing this pre-req.
    Explain what it means to bind a user or group to a cluster role.
    No need to show the ClusterRole or Role object definition at this point.
    steps to bind a user, a group, or an SA to a ClusterRole.
    Explain different between cluster-wide and per-namespace
    steps to bind a user to a role within a namespace
  • creating a custom role
    For this task, say that it is assumed the user is a cluster administrator.
    Explain rules and relation to REST paths.
    Task to create a new ClusterRole.
    Explain that all ClusterRoles can be used at cluster or namespace scope
  • editing a role
    How to add a new permission to an existing Role
    Move explanation of Auto-Reconciliation to this section as a warning about editing default roles.
  • delegating permission management to namespaces
    Explain Privilege Escalation Prevention
    Example: cluster admin creates namespace and grants admin to another user in that namespace. Then second user can grant to third in that namespace, but not escalate.
  • migrating from ABAC to RBAC
• a smaller reference section, which would include the default roles and bindings.

ℹ️ Clearly signpost anyone visiting https://kubernetes.io/docs/reference/access-authn-authz/rbac/ to the related task and concept pages that are added.

Optional: add a tutorial page too

Why is this needed
https://kubernetes.io/docs/reference/access-authn-authz/rbac/ is a long document that (currently) mixes conceptual, reference and task-focused documentation.

Comments
/sig auth
/sig security
/language en
/kind cleanup
/lifecycle frozen
/priority important-longterm

Replacement for issue #2792

[liggitt]

/kind documentation

[savitharaghunathan]

cc: @vinayakankugoyal

[sftim]

Oh, and

/triage accepted