Open Stack

Good day.

We trying to create middleware to restrict downscale of disks, and here 
few questions:

1) There is 'v3' API for nova in api-paste.ini, but I found no any 
documentation about 'v3 nova api' on api.openstack.org, and 
horizon/nova-pythonclient use v2 only. What is this? Is middleware for 
v3 differ from v2?

2) In api-paste.ini there is typical construction for middlewares:

use = call:nova.api.auth:pipeline_factory
noauth = faultwrap sizelimit ...
keystone = faultwrap sizelimit authtoken keystonecontext ...
keystone_nolimit = faultwrap sizelimit authtoken keystonecontext ...

What is those directives (noauth, keystone, keystone_nolimit)? I 
understand their meaning by names, but what exactly they means and which 
line is used for processing requests?

Are they related to auth_strategy=keystone in nova.conf?

Thanks.