Standard for identifying tenants in a multi-tenant deployment

As a cloud computing platform, OpenStack must support the concept of multi-tenancy. A common approach to organizing resources by 'tenant' across services is needed to be able to correlate usage tracking, auditing, authorization, etc... And within each multi-tenant service, the ability to identify each tenant's resources (for various reasons such as security, accounting, isolation, etc…) is also key. However, the definition of a 'tenant' will vary by operator and by deployment. This blueprint therefore proposes creating a lightweight standard for service developers to implement tenancy and resource grouping without a-priori knowledge of billing and accounting processes specific to the operator of an OpenStack deployment.