Document the importance of properly RBAC configured privileges.

[jvanz]

Document the importance of properly RBAC configured privileges.

It's necessary to document the importance of properly configured RBAC privileges to keep the admission control, and by consequence the Kuberwarden, secure and working as expected. Therefore, only the right users should be allowed to manipulate webhook objects and CRD objects. This is the mitigation action proposed in the threat #4 and #11

NOTE: This is an issue created from RFC discussing the admission control threat model. It's created to allow the Kubewarden team discuss the proposed mitigation further and select each individual item when necessary.