---
features:
  - |
    Adds a new ``generation`` column to the consumers table. This value is
    incremented every time allocations are made for a consumer. The new
    placement microversion 1.28 requires that all ``POST`` and ``PUT
    /allocations`` requests now include the ``consumer_generation`` parameter
    to ensure that if two processes are allocating resources for the same
    consumer, the second one to post doesn't overwrite the first. If there is a
    mismatch between the ``consumer_generation`` in the request and the current
    value in the database, the allocation will fail, and a 409 Conflict
    response will be returned. The calling process must then get the
    allocations for that consumer by calling ``GET /allocations/{consumer}``.
    That response will now contain, in addition to the allocations, the current
    value of the generation value for that consumer. The calling process should
    then combine the existing allocations with the ones it is trying to post,
    and re-submit with the current consumer_generation.