Public Volumes

(smcginnis): Marking obsolete as this has been sitting out there for a long time. If this is still needed, please submit a new bp.

Implementation plan:
  - Add field `is_public` (boolean) to `volumes` table in Cinder DB
  - Add support of `is_public` parameter in create and update operations in Cinder API
  - Add support of `is_public` parameter in create and update operations in Cinder CLI client (python-cinderclient)
  - Modify logic of the following operations: list volumes, get volume, attach volume. Allow the operations to be executed for users from another tenant in case if volume has `is_public`=true. (Using policy mechanism and additional constraints in DB API)

@griff: Don't see how this is different than the transfer feature tha's already implemented: volume-transfer

@dstepanenko: This feature was designed as a part of shared-volume feature implementation https://blueprints.launchpad.net/cinder/+spec/shared-volume. The main use case here is not to change ownership of a cinder volume, but to share it between many owners. We need this capability to be able to attach cinder volume to multiple instances simultaneously. Also there is one more use case - boot multiple instances from single volume

@griff: Oh, excellent... yes, I didn't know that you were interested in that change :)

Gerrit topic: https://review.openstack.org/#q,topic:bp/public-volumes,n,z

Addressed by: https://review.openstack.org/35261
    Add an ability to create cross-tenant visible (public) volumes.

<griff>: This appears to have been abandoned, removing from Havana

ogelbukh: I guess that 'public volume snapshots' feature could have broader use case.