Access.md added.

Some thoughts around identity and access management.  
Ideas still rough, but trying to share early.  Comments welcomed.

Some of this maybe should go into docs/security.md
My thinking has reached a point near what you just said.


The apiserver may cache Authz server responses for speed.  Cache lookup would be keyed on user, as well as other context.  So, APIserver needs to see user.

Yes, pluggable auth(n) and auth(z) would have a lot of benefits.  It would allow groups to chose between RBAC and ABAC, or even use one or the other on a per-project basis.

The one drawback I see is that if we want config to grow to include creation of not only objects but also policy (as Amazon cloudformation allows) then you'd like a single type of auth(z).  But, I think the immediate benefits of decoupling outweigh the minor drawback of config+policy portability.