Placement API microversion 1.19 enhances the payloads for the `GET
/resource_providers/{uuid}/aggregates` response and the `PUT
/resource_providers/{uuid}/aggregates` request and response to be
identical, and to include the ``resource_provider_generation``. As with
other generation-aware APIs, if the ``resource_provider_generation``
specified in the `PUT` request does not match the generation known by
the server, a 409 Conflict error is returned.
Change-Id: I86416e35da1798cdf039b42c9ed7629f0f9c75fc
blueprint: placement-aggregate-generation
3216f078d4