---
upgrade:
  - |
    The resource backend cannot be configured to anything but SQL if the SQL
    Identity backend is being used. The resource backend must now be SQL which
    allows for the use of Foreign Keys to domains/projects wherever desired.
    This makes managing project relationships and such much more straight
    forward. The inability to configure non-SQL resource backends has been
    in Keystone since at least Ocata. This is eliminating some complexity
    and preventing the need for some really ugly back-port SQL migrations
    in favor of a better model. Resource is highly relational and should be
    SQL based.